Which 6550 for SVT reissue?
roger
I'm intending to retube my ampeg svt classic (reissue) with either
sovtek 6550we's or the electro harmonix 6550's. They're both priced
about the same, which would be the better choice? Thanks.
J. Vincent Collins
only tube for that amp is the GE 6550A,, Jim McShane has a fine stash.
In ADVANCE
FUCK THE POLISHED TURD
Yup,, that's you FAT WILLIE
VIN COLLINS
"roger" <acid...@hotmail.com> wrote in message
news:5e1c0293.04021...@posting.google.com...
ACLARKE3
I do agree that the GE 6550's that Jim has are fine tubes and will last a very
long time.
Clarke
Subject: Re: Which 6550 for SVT reissue?
>From: "J. Vincent Collins" Packet...@att.net
>Date: 2/19/04 7:58 PM Eastern Standard Time
>Message-id: <4ZcZb.53758$hR.11...@bgtnsc05-news.ops.worldnet.att.net>
Jim Anable
> Put some real tubes in that prick,, Don't listen to the Turd Mongers,, the
> only tube for that amp is the GE 6550A
BIG second on the above ^^^
Rich Koerner
It was not uncommon for a set of GE-6550A's to last over five years of heavy full time
professional use during the Magnavox years of SVT.
The best tubes ever made for an SVT or 400-PS.
FYI, http://timeelect.com/6550a-ex.htm
Regards,
Rich Koerner,
Time Electronics.
http://www.timeelect.com
Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers
Lord Valve
J. Vincent Collins wrote:
> Put some real tubes in that prick,, Don't listen to the Turd Mongers,, the
> only tube for that amp is the GE 6550A,, Jim McShane has a fine stash.
>
> In ADVANCE
>
> FUCK THE POLISHED TURD
> Yup,, that's you FAT WILLIE
>
> VIN COLLINS
I also have a fine stash of NOS GE 6550A. Excellent tube.
Sometimes, however, folks are short on cash and can't
spring for NOS. The Sovtek 6550WE is a good choice;
in fact, there are people who prefer the tone of the Sovtek
over the GE. (Horrors!) One of those people is Tod Smallie,
bassist for the DTB (and the Yonrico Scott Band, which just
released their first CD) who is now going on three years
of 200+ dates per year with the same set of Sovtek 6550WE
I installed when I rebuilt/tweaked his 1973 SVT head (and sold
it to him).
It's all a matter of taste. Mine, in fact, runs to the Tung-Sol;
as far as I'm concerned, in my bi-amped 122 Leslies there
is Tung-Sol and then there's everything else. No tellin'
what folks might like.
Have a nice day, son.
Lord Valve
Tone Chaperone
VISIT MY WEBSITE: http://www.nebsnow.com/LordValve
I specialize in top quality HAND SELECTED NOS and
current-production vacuum tubes for guitar and
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Be a MAN...and buy some TODAY!"
Who's Drivin?
I also had 6 GE 6550's in my old Fender 400 PS. They will last a long, long
time.
Dave
lbrt...@aol.com
You are fortunate: the 6550 is a very rugged tube and any brand that
is not poorly made in China etc. is about equally good, it's a hard
tube to screw up & still meet spec. Take LV's suggestion, ignore the
snobs & try the Sovteks from him, you'll be happy and not broke.
Naked Clarke
What period do your GE 6550's date from? Are they all stamped Rivera?
Were they assembled in the USA?
Clarke
<detr...@ix.netcom.com> wrote in message news:<4035B251...@ix.netcom.com>...
J. Vincent Collins
SNOB!!!
This sonofabitch calls US a snob!!!
YOURE GODDAMN RIGHT!
Take those turds and put em in the friggin TERLET where they belong!! :-)
LOL
Just felt the need to poke a stick into the cage of the Turd Mongers.
Vin Collins
The Anti-Turd
<lbrt...@aol.com> wrote in message
news:205ef942.04022...@posting.google.com...
Rich Koerner
EXCUSE ME!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Are you in some way trying to say service life, and sustained high performance level IS,
or is NOT reflected in that cheaper price!!!!!!
The 6550WE in a Twin Reverb is one thing!!!!
In an SVT or 400-PS, it is totally an other world.
The 6550WE is NO GE-6550A. It's not even close!!!!!!!!
Sonically, or electrically.
For the bass player who has that, I'm going to push this amp till it blows attitude, where
the amp has to fill the club, the GE-6550A is the only tube to use.
BUT, if you are one of those bass players who plays before that threshold, and have a DI
and mic on the speaker cab, feeding a concert level house sound system, 6550WE's work ok.
It depends on if the bass player shakes the house with HIS Bass amp, or the sound system
shakes the house for him from the DI, then his amp really becomes HIS bass stage
monitor,...
which tube is better for the application!!!!!!!!!
Fred Nachbaur
J. Vincent Collins wrote:
> Snob?
>
> SNOB!!!
>
> This sonofabitch calls US a snob!!!
>
> YOURE GODDAMN RIGHT!
>
> Take those turds and put em in the friggin TERLET where they belong!! :-)
> LOL
>
> Just felt the need to poke a stick into the cage of the Turd Mongers.
>
>
> Vin Collins
> The Anti-Turd
> [...]
To paraphrase an old saying, "One man's turd is another man's treasure."
It's all so subjective. Haven't you ever met a guitarist who treasured
nasty old 12AX7's with gain out the bottom and just the barest breath of
emission, because they sound so (choose your description) <cool and
crunchy> -- <ballsy> -- <just like hendrix, man>.
Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+
RonSonic
>
>
>J. Vincent Collins wrote:
>
>> Put some real tubes in that prick,, Don't listen to the Turd Mongers,, the
>> only tube for that amp is the GE 6550A,, Jim McShane has a fine stash.
>>
>> In ADVANCE
>>
>> FUCK THE POLISHED TURD
>> Yup,, that's you FAT WILLIE
>>
>> VIN COLLINS
>
>I also have a fine stash of NOS GE 6550A. Excellent tube.
>
>Sometimes, however, folks are short on cash and can't
>spring for NOS. The Sovtek 6550WE is a good choice;
>in fact, there are people who prefer the tone of the Sovtek
>over the GE. (Horrors!) One of those people is Tod Smallie,
>bassist for the DTB (and the Yonrico Scott Band, which just
>released their first CD) who is now going on three years
>of 200+ dates per year with the same set of Sovtek 6550WE
>I installed when I rebuilt/tweaked his 1973 SVT head (and sold
>it to him).
>
>It's all a matter of taste. Mine, in fact, runs to the Tung-Sol;
>as far as I'm concerned, in my bi-amped 122 Leslies there
>is Tung-Sol and then there's everything else. No tellin'
>what folks might like.
I am amazed at how old those amps get before I see them needing tubes. Those
ancient Tung-Sol kick ass. I haven't seen NOS on them, is there any supply these
days?
Ron
claudel
I have 3.
:^)
Claude, who one day will finish the set
and install them in his SUNN 2000S.
WakyAmps
news:40369CAB...@timeelect.com:
>
> The 6550WE is NO GE-6550A. It's not even close!!!!!!!!
>
> Sonically, or electrically.
>
Not even close Rich? Got sounds samples or RTA traces to back
that one up?
Mind you, you have my utmost respect, but I think you're being a
bit of a zealot here. Ferinstance, when I push the (also very
expensive) 7581As for old Fender 6L6 setups, they're different
and you can tell, but it'd be a helluva stretch to say "not even
close".
Fer me anyway, sonically and _electrically_ not even close for a
6550 (but still keeping among power tubes) would be an EL84.
Maybe an EL34?
Lord Valve
Naked Clarke wrote:
> Willie,
>
> What period do your GE 6550's date from? Are they all stamped Rivera?
I have some stamped Rivera, some with regular GE print.
> Were they assembled in the USA?
Sure. I didn't know there were any that *weren't.*Where would they make 'em besides
the USA?
LV
Rich Koerner
WakyAmps wrote:
>
> Rich Koerner <ri...@timeelect.com> wrote in
> news:40369CAB...@timeelect.com:
>
> >
> > The 6550WE is NO GE-6550A. It's not even close!!!!!!!!
> >
> > Sonically, or electrically.
> >
>
> Not even close Rich? Got sounds samples or RTA traces to back
> that one up?
Don't NEED to. Any one standing in the room listening to the sound of the bass coming off
the stage will tell you the difference. Just put them up there side by side.
Not to mention the test bench tells the story.
With a stock 400-PS, I have to mod the damn thing to keep it from smoking the
6650-WE's!!!!
And, after that is done, they can't even get the output of the 400-PS to stock rated 435
watts output on the three loads required!!!!!!!
Then, after used in for a few months of gig playing on it as a hard ass POWER PLAYER, put
it back on the bench, and see where things sit on the test loads again.
BTW, that spec is 435 watts R.M.S. at *50* Hz. Clean sine wave before clip!!!
That sine wave looks a little squirrelly down there with those WE's.
What does an SVT do at that 50 Hz with 6550-WE's after the same
treatment!!!!!!!!!!!!!!!!!!!!!
> Mind you, you have my utmost respect, but I think you're being a
> bit of a zealot here.
No, I'm none of that.
I'll tell you what I am though.
I'm a kick your ass bass player ALL my life. There is nothing timid of shy when it comes
to my bass providing the horsepower in the songs to ROCK the HOUSE, when I'm on stage in a
formal band!!!!!!!!!!!!!!!!!
I played the Big amps and the Stacks, when they were in fashion. And, the SS crap bass
players use today, with that freaking in your face EQ'd sound, is NOT my idea of what bass
is all about!!!!
I'm old school, and not about to change any time soon!!!!!!!
Big fat gut bottom that rumbles through the club's walls into the parking lot, without
getting in the way of the band in the house, is what I'm all about.
But, that is not what today's bass player is all about, with his in your face bass rig
that falls on it face when I hit my neck pickup on my 66 bass, and the amp hits clip
trying to get down below the low end roll off.
That place below the roll off, IS where the freaking BASS belongs in the MUSIC.
Even Willie knows what FAT BOTTOM from a B3 is all about.
Ask him if He'd like to slap a 10" power piston in a 122, and not find the low end
fundamental rolling around the room on the floor soft as a pillow. But NOW, it's IN YOUR
FACE, where you HEAR it, and DON'T *FEEL* IT!!!!
400-PS amps present the bass like I like it. And, it takes TWO, not one, but TWO killer
setup SVT's with GE's and FOUR 8x10" cabs to equal tricked up 400-PS.
And THAT, is FACT. Rich gray's band opened for Black Oak Arkansas using one of my tricked
up 400's and four custom cabs. Black Oak had the Ampeg endorsement, and the bass player
had the SVT's.
But, after the first show, their bass player comes up to Richie, and asks if he could use
the 400-PS for the rest of the tour. I know its fact, because Richie called me for my
opinion. I said, let him do it. What the hell, have fun.
Later, that same 400-PS got people sick in the Filmore East from the low end of an ARP
synth.
If there is one thing I know, and have experienced, is the power of the Big Bass Tube
Rigs.
I've lived it, when most you guys were either doing something else, or weren't on the
planet then.
I had my vision blurred standing in from of a dual SVT stack playing Sunshine of your
love, when the record broke. BTW, that's two SVT heads, and four 8x10 cabs.
So, till you been there and done it, what are you going to tell me about it!!!!!!!!
I can't wait for things to come together where Kent and I can have some fun doing a stack
gig, doing it ALL exactly the way Jimi did it, so some of you all can *EXPERIENCE* the
Experience, as people did when a lot of you all MISSED it!!!!!!!!!!!!!!!!!!!!
> Ferinstance, when I push the (also very
> expensive) 7581As for old Fender 6L6 setups, they're different
> and you can tell, but it'd be a helluva stretch to say "not even
> close".
I ain't talking 6L6's, you are.
When it comes to 6L6's, My purple monster blows away 900's and 2000's in front of their
owners, when comparisons are done.
Then, you should SEE the look on their faces, when I pull the purple monster stack away
from the wall and turn it around, and all they SEE sitting the sockets are a PAIR of OLD
GE-6L6GC's!!!!!!!!
Yeah, NO SHIT!!!!!!!!!!!!!!!!!!!!!
Now, that is no brag, fantasy, or drugs talking.
It's just MY reality!!!!!!!!!!!!!
And, anyone is free to stop in the shop, step into my reality, and EXPERIENCE It, for
themselves!!!!!!!
Look, I've heard people talking their shit, and it comes off like they are on the same
page as I am.
BUT, when you are in the room with me and my gear, it's a whole different
world!!!!!!!!!!!!!!!!!!!!
And then, you will know, I'm in whole different place that really exists, where the music
becomes a whole different kind of spirit, which moves people, because they can *feel* it.
Yeah, the clubs are smaller, and the sound man tells ya to TURN IT DOWN, for that 5000
watt house system.
Yeah, you weak back guys want your air boxes with all that gain, so you can get a piece of
what I'm talking about. But that's all you're EVER going to get. Is just a freaking
SMALL piece.
You ain't going to FEEL it. Or what it FEELS like to SMOKE the SET, and SMOKE the crowd,
as the Music Takes You, and THEM Higher!!!!
Those are not just lyrics to a song, they're REAL!!!!!
The MUSIC, alone, really DID, take YOU, HIGHER!!!!!!
Not like today's music tries to, with the sound of PROCESSED Guitar sounds.
THAT'S, freaking Bull Shit!!!!!!!!!!!!!!!!!!!!!!!!
> Fer me anyway, sonically and _electrically_ not even close for a
> 6550 (but still keeping among power tubes) would be an EL84.
> Maybe an EL34?
That's so small a piece, you can't even get an idea of what I've experienced on the stage
from the music.
Most importantly, there ain't enough in the written or performed MUSIC, to take even a
garden slug higher with that on the stage, for today's reality.
<After thought>
There is one man *out there* more than me.
Bootsy uses 15 KW Crown power on stage when he plays. No Less!!!!!!!!!!!!!!!!
How do I know this,...... look.
http://timeelect.com/Book22.htm
There you go.
GE-6550A's, ain't got no equal with the numbers 6550 on the glass!!!!
The 400-PS, is the test bed for that shit!!!!
It was designed for it!!!!!
http://timeelect.com/6550a-ex.htm
CASE CLOSED!!!!!!!!!!!!!!!!!!!
ACLARKE3
assembled in the far east towards the end of the '80s. Old KY parts? Don't
know.
Clarke
>Subject: Re: Which 6550 for SVT reissue?
>From: Lord Valve detr...@ix.netcom.com
>Date: 2/21/04 3:28 AM Eastern Standard Time
>Message-id: <4037184A...@ix.netcom.com>
Patrick Turner
Rich Koerner wrote:
It is with interest I read your ideas about providing music
with feeling, rather than with false edgy sounding fake bass.
I also see the Fender 400 watt amp you refer to has only 6 x 6550
tubes to make the 400 watts, which means 133 watts per pair of 6550,
which is rather a lot of stress on the tubes, regardless of the brand of tubes used.
When such an amp is is pushed into over drive one would think
that screen currents and grid currents could be rather high,
and the danger of tube damage would be ever present,
especially if someone connects too many speakers accidentally.
Ever thought of using a dozen 6550 to do the job?
This reduces the power per pair to a more survivable 66 watt.
Audio Research use 16 x 6550 for their Reference 600,
and that 75 watts per pair, same as a humble McIntosh.
See http://www.turneraudio.com.au/htmlwebpgs02/300monobloc.htm
to see a sample.
My amps make about 200 watts of class A, and its all very relaxed
and the idea is to have limitless headroom for a hifi situation,
where effortless and distortion free sound is sought.
In one of my 8585 hifi amps, I used 8 x jan GE6550, nos, green lettering.
They were about twice the price I pay now for EH6550.
I don't know wherther there was anything really special about them.
After 7 years of on -off use in a hifi situation, they all became prone to
grid current even at idle, and some of the grids going a volt or two positive.
Then I reduced the bias resistors to 100k, and they held their bias better.
The client had me replace all the tubes with EH 6550,
and he said there was a big improvement in the soundstage,
which seemed to have depth, not only width, as before with GE,
then he said the dynamics and detail were improved.
Hifi amps are never subject to severe signal overloads and gross clipping
with rock musician amps.
But they are left running for hours on end, day after day,
with a substantial bias current to allow lots of class A.
I guess the tubes wear out for different reasons in the
music amp versus the hi-fi amp.
One of the sweetest music amps I heard was 6V6 PP,
about 80% UL taps, nearly triode, in class A.
Another 6V6 in triode drove the output stage via a transformer.
This amp was one of the few which seemed to have sweetness
and a sort of natural reverb, but without a reverb unit used.
The owner-builder was a physics lecturer, whose interest off campus was guitar,
and rocket engines.
Another client uses Sovtek 6550 in triode in a Marshall head for use
in his "dark metal" band, and the sound is basically like a continual stream
of jumbo jets crashing on the pavement in front of you.
Not my cuppa tea, but some folks think its very cool!
The tubes are either off, or 40 dB over clipping.
After 4 years, I think he's on his second pair......
The first pair expired after using too low a load impedance
when swithed to the 16 ohm setting.
So when I hear about tubes failing, I wonder first
about the human element.
Unlike Fender, I fit individual cathode current sensors
to each output tube so that if any one tube out of so many
misbehaves, and goes red with too much cathode current,
the amp is turned off.
That mightn't suit a muso, who might prefer to blow a few tubes rather than stop
to change to a spare amp between songs, if the fuse hasn't blown.
Patrick Turner
Patrick Turner
WakyAmps wrote:
Doesn't the way the tubes are set up affect the sound?
EL84 in a Vox AC30 sound sweet as, and smooth tubey over drive,
because its real class A.
In some other amp with higher B+, and lower idle current
for near class B, they ain't so good.
I some how think it ain't what you got that is everything,
but the way you use it!
Patrick Turner.
WakyAmps
news:40377033...@turneraudio.com.au:
Yes, how it is set up makes a huge difference, no a Vox AC-30
isn't really class A.
My point was (and continues to be) that Rich is describing
GE6550s vs Sovs as if they came from a different planet. I'm
guessing further (though Rich hasn't explicitly said so) that
he'd classify the Sovs as polished turds. I'm merely suggesting
that, while for Rich there's no other tube than the GE and no
other amp than the PS400, the OP is looking to retube a reissue
SVT and the OP may be quite satisfied with the Sovs (at half
the price no less). And it is the OP's needs we're trying to
address here, right?
The 6L6 comparison wasn't meant as a comparison of 6L6 vs 6550,
but to serve as an example of gradation between similar tubes.
Remember, Rich claims that the GE and Sov "aren't even close"
sonically or electrically. Maybe so in his tweaked 400PS and to
his ears and playing style; there may not be as strong a case
in the OP's RI-SVT and to the OP's ears and style.
TD Madden
Seems I read some where that AC-30s aren't "really" Class-A....anyone
have the scoop?
JTM50
tdmadd...@spam-comcast.net wrote on 2/21/04 8:03 AM:
Yes do a google search since this has been discussed to death numerous
times.
Aiken's site also discusses this in depth...
Lloyd
to...@nospamprepair.com
Winged C 6550C How come?. We use plenty of these in repairs and lot's in
SVT's with very good results. They aren't GE's or Tung Sol's either but they
hold up well over time and sound pretty damn good. My 2c
Todd
Patrick Turner
WakyAmps wrote:
The ones I have serviced were class A,
with absolutely no feedback.
They had a high bias current, and each of the 4 EL84 draws about 12
watts
at least at idle.
>
> My point was (and continues to be) that Rich is describing
> GE6550s vs Sovs as if they came from a different planet. I'm
> guessing further (though Rich hasn't explicitly said so) that
> he'd classify the Sovs as polished turds.
I have not used enough 6550 in guitar amps to know
who is right here.
The 6550 and KT88 are capable of 140 watts per pair,
and to me that's a recipe for unreliability.
From what I have seen the russian 6550 from EH
is exactly the same internally as the EH KT88 or smaller bottle sovtek
KT88. It seems as though EH have rationalised the construction of
these two tube types, and the only thing different is the packaging,
ie, the glass bottle and lettering is nicer on the more expensive 6550
and KT88.
I don't care that they seem to have done this, as I quite like the
6550/KT88
being currently made.
As I see it, all the 6550 from yesteryear about which ppl rave as being
just so superior to
anything else are all actullay prone to failure from hard use,
unfortunate
events with the wrong speaker impedance, etc, since all the ratings
indicate that they are what they are, mortal tubes, and like us mortal
human beings,
they are gonna die one day.
> I'm merely suggesting
> that, while for Rich there's no other tube than the GE and no
> other amp than the PS400, the OP is looking to retube a reissue
> SVT and the OP may be quite satisfied with the Sovs (at half
> the price no less). And it is the OP's needs we're trying to
> address here, right?
I assure you that other folks make big tube amps.
As new old stocks of favourite old tubes dry up, all we are gonna have
is sovtek, EH, Svetlana etc.
But asking more than 75 watts per pair of bottles is asking for trouble.
>
>
> The 6L6 comparison wasn't meant as a comparison of 6L6 vs 6550,
> but to serve as an example of gradation between similar tubes.
Indeed.
Some 6L6 were far better than others, and I forget now who
used multi layer material in the anodes to prevent red hot spots,
which meant that the whole anode ran at much closer to the same temp,
which meant an effective 30 watt diss rating, instead of only 22 watts.
In the wrong circumstance, the screens would still melt anyways.....
>
> Remember, Rich claims that the GE and Sov "aren't even close"
> sonically or electrically. Maybe so in his tweaked 400PS and to
> his ears and playing style; there may not be as strong a case
> in the OP's RI-SVT and to the OP's ears and style.
How anyone can tell much difference between the sound of
tubes when the thd is at around 25%, and IMD at around 50%
is beyond me.
I once repaired a Lennard aus made 400 watt PA amp with inputs
for 4 performers. It ran on a 900 volt supply, 450volt screen supply,
with 8 x EL34,
so the power per pair was 100 watts.
But it kept spitting smoke and tubes out.
I then examined the dude's speakers.
He had two bins each with 6 x 12" speakers, which he said were 8 ohms,
but he hadn't said he'd re-wired them all together in parallel some
years before!
He'd been sending more power into the cables than to the speakers,
and had been labouring on for years with only 50 watts from the amp
with a load of about 3/4 of an ohm.
But when he went to do open air gigs, he needed more volume,
and poof went these tubes.
He had 4 different brands plugged in when I first saw the amp,
Mullard, Telsla, chinese, and Miniwatt.
I rewired his speakers so that they all were series/parallel for 8 ohms,
and rewired the amp B+ to an available lower HT tap on the PT,
and placed a separate bias pot for each output tube,
replaced all the tubes for sovteks,
and revised the FB for a useful 12 dB, and placed RC snubber
networks across the 1/2 primaries of the OPT,
and thus made it impossible for RF to start when tubes glowed red,
and burning out quickly.
Power is now limited to 250 watts, and I have not heard from this guy in
4 years,
so I guess the amp is going OK.
Such an amp runs nearly all in class B, with a low bias current, so idle
diss for each tube is about only 16 watts, but at
about 2/3 max po the diss goes beyond the rated 28 watt max,
but because the duty cycle is low, ie, the signal isn't a continuous
sine wave,
the tubes survive, providing there is nothing wrong with the load value.
In this case, its better to err on the load value by choosing a value
too
high, rather than too low!
Most of my experience is with hi-fi usage, when thd is only 0.02%.
Even then you *can* here a difference between tubes despite very
similar measurements of thd/imd, etc.
The change of brands of tubes in preamps makes just as big a difference.
I know there are times when "kick ass bass" is a must, and the sound
system
at the film club I go to provides this when you hear a train going past
nearby.
Not a tube amp to be seen. Its all SS behemoths, perhaps several 1,000
watters,
but sure, you feel the sound, as well as hear it, and ear plugs are
required
by folks such as I with such movies made deliberately to be sonically
provocative,
because the technology is the focus, to disguise the attrocious acting,
gadgets used to prop up otherwise failure prone humans,
with special effects every minute, and even with sharks growling
underwater.
I am appalled at such idiotic stories about tomb raiding, and all the
sound engineering
is in vain, as its an attempt to deafen me, ie, injure my hearing.
I have visited very briefly some indoor venues in university canteens
where they had several
thousand watts of amplification. Even with ear plugs, it was quite
impossible for me
to enjoy anything I saw, heard, or smelt, and my chest heaved with the
bass,
and at every amplified drum beat.
I have to agree that some SS set ups *do* sound quite loud.
I don't like it that loud, and never have, but to some folks whose ears
are not yet
"matured", such excess sound is somehow cool.
I often wonder if the use of tube amps in theatres would soften the
often
appallingly harsh sound tracks, where the cowboy alteration of recorded
sound has routinely
been compressed, noise filtered, de-essed, eq'd unaturally, etc.
I quite like classical music which is 200 years old, and my local town's
orchestra has about 40 players, and the bass from the two, perhaps
three
entirely unamplified acoustic bass violins plus a couple of various
drums
is entirely adequate to form a foundation for the music.
The levels attained are entirely sufficient to fill my senses, and
transport
my mind away where the composer wants to take it.
The use of electricity over the last 50 years, by a handful
of groovy, cool, awesome, whatever types on a stage who obviously
have never been to music college has not made concert going
any better for me. Rolling Stones concerts with 140,000 watts
and 250,000 people are to me quite boring/irritating events I wouldn't
be seen dead at.
I probably wouldn't have turned up at the Colleseum in Rome
in AD 100, to watch and hear christians being fed to lions,
and to witness the mayhem of the chariot races, and the fight to the
death
gladiator battles. All too gross.
Another 1,500 years had to pass before music evolved which
I could really be entranced by, because of its lack of repetition,
complex music structure, and complete absense of peurile wailings
about "lerve" et all.
Its hard to get much volume from a hard bodied electric guitar,
so an amp is essential, but if anything in this electronic age
is used so often to excess, apart from drugs and grog, it has to be the
sound amp.
I am quite happy with someone sitting 30 feet away, using about 2 watts,
and who really knows how to play some real blues, and whose amp
sounds inviting, warm, musical.
Patrick Turner.
roger
this torrent of bullshit. Has anyone anctually used the EH 6550s in an
SVT? I've seen some good reports from the hi-fi guys.
ps I run an ampeg 410hlf most of the time and mic/di the amp when the
gig requires it.
dw
Great post, Patrick.
thanks,
dw
Miles O'Neal
>> Yes, how it is set up makes a huge difference, no a Vox AC-30 isn't
>> really class A.
>
> The ones I have serviced were class A, with absolutely no feedback.
> They had a high bias current, and each of the 4 EL84 draws about 12 watts
> at least at idle.
Now this doesn't make any sense at all.
In Class A, full tilt isn't different
enough from idle to make any difference.
So, just curious - why do you say they
were Class A? What do you think that
means?
...
> As I see it, all the 6550 from yesteryear about which ppl rave as being
> just so superior to
> anything else are all actullay prone to failure from hard use, unfortunate
> events with the wrong speaker impedance, etc, since all the ratings
> indicate that they are what they are, mortal tubes, and like us mortal
> human beings,
> they are gonna die one day.
While this is true, some of the tubes made back
in the far exceeded their published specs, and
hence are worth far more than the common tubes
of today, to some people. If it'll last five
times as long when being punished, it's worth at
least five times the price - more if you calculate
the lower likelihood of failure during a gig.
>> I'm merely suggesting
>> that, while for Rich there's no other tube than the GE and no other amp
>> than the PS400, the OP is looking to retube a reissue SVT and the OP may
>> be quite satisfied with the Sovs (at half the price no less). And it is
>> the OP's needs we're trying to address here, right?
Sure. I agree with you here. At the same time
I understand where Rich is coming from. He's a
firm believer in the value of the old tubes over
anything built today (so far), and wants to help
others understand that.
In some case I agree with him on the state of the
art and the value; in others I don't. Most of the
time we're in different threads, because I mostly
deal with 6BQ5s and 6V6s, which he dismisses as
"radio tubes". 8^)
>
> I assure you that other folks make big tube amps. As new old stocks of
> favourite old tubes dry up, all we are gonna have is sovtek, EH, Svetlana
> etc.
> But asking more than 75 watts per pair of bottles is asking for trouble.
With the new tubes this may be so - I don't know.
But I have known lots of folks getting 100W or more
per pair (think SVT!) with no problem.
...
>> Remember, Rich claims that the GE and Sov "aren't even close" sonically
>> or electrically. Maybe so in his tweaked 400PS and to his ears and
>> playing style; there may not be as strong a case in the OP's RI-SVT and
>> to the OP's ears and style.
>
> How anyone can tell much difference between the sound of tubes when the
> thd is at around 25%, and IMD at around 50% is beyond me.
Just curios - are you a musician? Do you care about
tone? Do you consider your ears good? Because the
sonic differences in tubes are ell documented. My
wife and kids, none of whom play guitar (Josiah keeps
saying he wants to, but never practices much) can hear
these differences, and they aren't tube freaks by any
stretch of the imagination!
[Story of 0 ohm tube PA into < 1 ohm bins snipped]
> In this case, its better to err on the load value by choosing a value too
> high, rather than too low!
Why not try your friend's PA head into, say, 64
ohms at full blast and let us know how that goes?
-Miles
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
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Don
>I know there are times when "kick ass bass" is a must, and the sound
>system
>at the film club I go to provides this when you hear a train going past
>nearby.
>Not a tube amp to be seen. Its all SS behemoths, perhaps several 1,000
>watters,
>but sure, you feel the sound, as well as hear it, and ear plugs are
>required
>by folks such as I with such movies made deliberately to be sonically
>provocative,
>because the technology is the focus, to disguise the attrocious acting,
>gadgets used to prop up otherwise failure prone humans,
>with special effects every minute, and even with sharks growling
>underwater.
>I am appalled at such idiotic stories about tomb raiding, and all the
>sound engineering
>is in vain, as its an attempt to deafen me, ie, injure my hearing.
I suggest you see "Cold Mountain" an American Civil War movie, with folk
music.
Mystic River and Lost in Translation are two good adult films, no tomb raiding
involved.
JTM50
m...@rru.com wrote on 2/21/04 7:58 PM:
> Patrick Turner responded to WakyAmps, who said:
>
>>> Yes, how it is set up makes a huge difference, no a Vox AC-30 isn't
>>> really class A.
>>
>> The ones I have serviced were class A, with absolutely no feedback.
>> They had a high bias current, and each of the 4 EL84 draws about 12 watts
>> at least at idle.
>
> Now this doesn't make any sense at all.
> In Class A, full tilt isn't different
> enough from idle to make any difference.
>
> So, just curious - why do you say they
> were Class A? What do you think that
> means?
Yeah, and 12 watts on an EL84 is almost Ice cold!
My Guytron runs em at 17-18 watts static (45-50ma)!
Lloyd
WakyAmps
news:BC5D8EB5.E182%JT...@Shaw.ca:
> Yeah, and 12 watts on an EL84 is almost Ice cold!
> My Guytron runs em at 17-18 watts static (45-50ma)!
>
> Lloyd
>
Since max rated dissipation for an EL84 is 12 watts, I
wouldn't call it ice cold. I'd call 17-18 running the
bejeezus out of 'em[1]
However, static dissipation equal to max dissipation does not
necessarily mean class A.
[1] though 17-18 is a nice static point for class ab1 el-34s :)
JTM50
a...@ATSIGN.wakarusaamp.DOTSIGN.com wrote on 2/21/04 11:44 PM:
Yeah, well, in my experience with them in the Guytron[1] is they do hold up
to that punishment. I've used Sovteks, JJs and recently tried the EHs (they
are ok but that's it) and some NOS Bejings (that just SUCK).
I'm not saying that it's easy on them but they will last a reasonable amount
of time[2]...
Lloyd
[1] The Guytron has them in it's preamp coupled by a trannie to a resistive
load.
[2] about 6 months of good tone if you play everyday.
James Angelo Ruggieri, P.E.
maintain spacing and does not readily "short" when subject to
shock/vibration. This can be easily determined by energizing the amp with a
100 Watt clear light bulb in series with the line, and with all the tubes
installed, tapping on the tubes with a rubber handled screwdriver - while
observing the series line light for changes in luminance. Changes in the
light would indicate structurally unstable tube elements - meaning it is
likely the amp/tubes will short during service. Otherwise, I doubt you would
be able to discern any quality difference. The SVT is also tough to
balance - from what I recall, and can be very touchy.
Jim
--
JAMES RUGGIERI
"roger" <acid...@hotmail.com> wrote in message
news:5e1c0293.04021...@posting.google.com...
lbrt...@aol.com
> The 6550WE is NO GE-6550A. It's not even close!!!!!!!!
>
> Sonically, or electrically.
Pls clarify, Rich - R U saying that it doesn't dissipate well enough
under full load?
If so, what specific failures have you noted or had reported - i.e.
screen toasted or etc.? This wld be valuable to know, as well as the
conditions under which there was a failure, if available.
Yes we know the amp.
Electrically, it would be a stretch to make a distinction; unless the
mfgr is fraudulent or really lax, a spec is a spec..."not even close"
would seem to be a rash statement unless some mfgr's version sucketh
in specific, doccumented ways.
But it was/is not uncommon for some to run them above their 35w plate
dis at full power, which our old GE's sometimes tolerate somewhat (and
sometimes didn't or won't, as well).
None of us hv seen it all, in my case hv yet to see a crappy 6550 that
wasn't oriental.
Patrick Turner
Miles O'Neal wrote:
> Patrick Turner responded to WakyAmps, who said:
>
> >> Yes, how it is set up makes a huge difference, no a Vox AC-30 isn't
> >> really class A.
> >
> > The ones I have serviced were class A, with absolutely no feedback.
> > They had a high bias current, and each of the 4 EL84 draws about 12 watts
> > at least at idle.
>
> Now this doesn't make any sense at all.
> In Class A, full tilt isn't different
> enough from idle to make any difference.
The input power to the 4 x EL84 is around 48 watts.
In an ideal class A amp, a max of 24 watts in class A is available.
But usually, class A max efficiency is about 40%, so
expect about 20 watts of class A from 4 x EL84,
with a few extra AB watts to make it to about 30 at onset of clipping.
Such operation is substantially class A.
In a Musical Reference hi-fi amp made in the US, Ea = 700v, Eg2 = 350v,
and power output at clip from a pair is 36 watts, but its very definately
mainly class B, with only a couple of class A watts.
Idle power is about 5 watts per tube. During low level operation,
there is much more thd than for amps with gobs of class A power..
But nevertheless, the use of a high value RL seen by the tubes of 14k,
and 5% of CFB from a winding on the opt, and global FB, the amp
measures ok.
Many EL84 amps are less ambitious about power,
with a quite a few good for 21 watts, such as Mesa Boogie,
some Fenders with 6V6, where the B+ is high enough, as well as
the load value, to get such power, which is well in excess of what you'd get
if every watt was class A.
The Fender I fixed last week got 21 watts AB1 from 6V6, with 450v supply.
BIG voltage swing, low current swing, and mainly class B operation.
The cut off behaviour of tubes is such that the crossover distortion
of such amps is not entirely awful, certainly not in a guitar amp,
where distortions are prized, and there is no such thing as really
clean operation, because it sounds so plain dull and boring.
One is forced to allow some harmonic distortions, principally 3H,
and then boost the hell out of all the treble, add some reverb,
and maybe it sounds well.
Most guitar amps are PP mainly class B in their output stages.
Very few *pure* class A PP output stages are ever used, and
*extremely* few single ended class A output stages.
But all the input stages are nearly all SE stages using 12AX7,
so much of the warmth comes from the SE triode input stages which
are over driven a bit, and the distortion happens to be musically appealing,
( with a high level of 2H and 4H ), even to old smoothies, like George Benson.
But don't ask me what Mark Knoffler uses in his amp circuit to give him his
trademark sound.
>
>
> So, just curious - why do you say they
> were Class A? What do you think that
> means?
because they are substantially class A.
Not totally class A, but more class A than nearly all other amps
in the output stages.
>
>
> ...
> > As I see it, all the 6550 from yesteryear about which ppl rave as being
> > just so superior to
> > anything else are all actullay prone to failure from hard use, unfortunate
> > events with the wrong speaker impedance, etc, since all the ratings
> > indicate that they are what they are, mortal tubes, and like us mortal
> > human beings,
> > they are gonna die one day.
>
> While this is true, some of the tubes made back
> in the far exceeded their published specs, and
> hence are worth far more than the common tubes
> of today, to some people. If it'll last five
> times as long when being punished, it's worth at
> least five times the price - more if you calculate
> the lower likelihood of failure during a gig.
But none of the tubes I have seen will take 5 times the
power dissipation of an average spec tube.
There is *no* 6550 with an anode diss rating of 200 watts,
and nealry all turn red at just over 45 watts, and then its time for
prayer, or to reach for the off switch.
I actually like NOS US made tubes.
I have a pair of ancient 40 yr old Sylvania 6CA7,
which in UL still pump out 28 watts of class AB at
0.125% thd with 17 dB of NFB in an ancient ex school PA
amp which I use regurlarly in my shed to test speakers etc.
It withstands the occasional red plate session, when left running into
a load which is too low. Done that a few times.
Accidently had the leads come together for awhile with a signal,
and sure, it got hot, but good as new after being turned off for
5 minutes.
These tubes were old and tired when I bought 7 years ago sh for $3 each,
but they keep truckin. I know I ain't likely to
ever blow up a nice pair of customers speakers I happen to be testing,
simply because I'm usin a transformer coupled amp, and there is no nasty
DC to come a leapin outa the box to fry a driver.
I see no reason why today's tubes won't survive the "industrial use".
I have had one sovtek KT88 get a broken heater connection on a tube pin,
and this made the other in the PP circuit do all the work, and it went red
for quite some time before the customer noticed, ( customers are
non techs, and notoriously slow to realize something is wrong ),
but after a resolder, the overheated tube seemed undamaged.
>
>
> >> I'm merely suggesting
> >> that, while for Rich there's no other tube than the GE and no other amp
> >> than the PS400, the OP is looking to retube a reissue SVT and the OP may
> >> be quite satisfied with the Sovs (at half the price no less). And it is
> >> the OP's needs we're trying to address here, right?
>
> Sure. I agree with you here. At the same time
> I understand where Rich is coming from. He's a
> firm believer in the value of the old tubes over
> anything built today (so far), and wants to help
> others understand that.
>
> In some case I agree with him on the state of the
> art and the value; in others I don't. Most of the
> time we're in different threads, because I mostly
> deal with 6BQ5s and 6V6s, which he dismisses as
> "radio tubes". 8^)
The littlies have a very nice sound though, and its why dudes use them.
For a small venue for a jazz scene, maybe its all that's needed.
>
>
> >
> > I assure you that other folks make big tube amps. As new old stocks of
> > favourite old tubes dry up, all we are gonna have is sovtek, EH, Svetlana
> > etc.
> > But asking more than 75 watts per pair of bottles is asking for trouble.
>
> With the new tubes this may be so - I don't know.
> But I have known lots of folks getting 100W or more
> per pair (think SVT!) with no problem.
Back in the 1960's, quite a few amps using EL34 with
800 volt B+ supplies were used, mainly for PA, because
100 watts was available, and low THD wasn't a priority.
I probably sat thru many a sermon ( boring ) at the church
where I was taken each sunday as a kid with such amps.
Where are all those amps? all gone to the Yonder!
And these were all mainly used for just a bit of pious speach,
not kickass bass with serious overdrive.
Tube and socket replacements due to arcing were common,
so one reason they all were replaced was the spectacular
failures, costs of maintenance, and anyone selling the then very
new, and even rather expensive solid state amps had little trouble.
I don't believe they sounded all that much worse in the PA field.
Most of those have all expired and been thrown out.
Nothing is forever.
> ...
> >> Remember, Rich claims that the GE and Sov "aren't even close" sonically
> >> or electrically. Maybe so in his tweaked 400PS and to his ears and
> >> playing style; there may not be as strong a case in the OP's RI-SVT and
> >> to the OP's ears and style.
> >
> > How anyone can tell much difference between the sound of tubes when the
> > thd is at around 25%, and IMD at around 50% is beyond me.
>
> Just curios - are you a musician?
Not now; I was in a band many years ago,
and played acoustic 12 string. I did some time in coffee lounges
with folk music; I can stil play, but I have little time.
I often have to fix guitar amps, and I hear the musician's problems
and the sound, during testing....
> Do you care about
> tone?
Yes, and mainly at low levels, because at gross overload levels,
the waveform is mainly a square wave, and the difference in tube brands
does not make an enormous difference to the sound
of such energy being supplied to a speaker.
> Do you consider your ears good?
Good enough.
> Because the
> sonic differences in tubes are ell documented. My
> wife and kids, none of whom play guitar (Josiah keeps
> saying he wants to, but never practices much) can hear
> these differences, and they aren't tube freaks by any
> stretch of the imagination!
I hear differences, sure, but mainly at low levels.
The "dark metal" guy who likes his 6550 in triode runs them at
gross overload all night. I don't believe the sound would change
if he changed from Sovtek to GE.
To me it would still sound like a continuous aeroplane crash
happening right in front of me.
>
>
> [Story of 0 ohm tube PA into < 1 ohm bins snipped]
>
> > In this case, its better to err on the load value by choosing a value too
> > high, rather than too low!
>
> Why not try your friend's PA head into, say, 64
> ohms at full blast and let us know how that goes?
If you have a 400 watt amp capable of 400 watts into 64 ohms,
then using 64 ohms would give only a fraction of the power,
and the sound level, because the voltage swing from the tubes is
nearly maximum even with 8 ohms, at 56 vrms, and
with 64 ohms, only 20 more swing is available, ie 67 volts,
so one gets only 70 watts. But the class A % would be quite high.
Pentode/tetrode operation is almost universally used for output stages
in the music industry in tube amps.
Distortion in such amps with a high RL is not necessarily
all that much lower than some lower value RL which is the optimal for
low thd. But high value RLs mean the output stage has much higher gain.
If there is a feedback loop, then there is effectively much more applied FB
with a high value RL.
The gain of a 6550 in class A with a 2 kohm plate load is about 19.
But with 16k its about 80+, or five times the gain, which is + 14 dB.
If there was 12 dB of FB applied with 2k, then there is about
5 times the feedback applied when the load is changed to eight times the load
value.
Thus with 16k, there is an effective 26 dB of FB applied.
One has to be careful about stability if using a high value load, lest the amp
begin to oscillate at some LF or HF.
In practice, since most amps operate mainly in class B,
the open loop gain is about 1/2 what I have described, so the max amount of
FB with a 64 ohm load would be 20 dB at high power.
But at low power, the gain is higher, since it is class A.
This explains why some poorly stabilised amps oscillate just a little
and no more, because they do so only in the operating region where the tube gain
is high.
Speaker impedances rise to high values at HF, because of their
inductive character.
So, I would never recommend that anyone use a 64 ohm load with
a pentode/tetrode amp which was designed for 8 ohms.
16 ohms would be OK though, but 4 ohms could be deadly.
To ensure stability, even with no load at all, when the output tube
gain is perhaps 150+ then the feedback loop has to be carefully
considered, and some way of damping, ie, loading the output stage
at F above 20 kHz should be employed,
say by having an RC network with HV rated C and large wattage R
strapped across each 1/2 primary.
Some ancient amps using V1505 power triodes with 2 kV B+,
good for 1,100 watts class AB2 used adjustable spark
gaps to allow arcs to occur if the anode to anode signal voltage exceeded a
certain
level. Little FB was used. That was the primitive approach.
But with pentodes or tetrodes, unlike triodes, the gain changes with load,
and often some FB is used. Well concieved RC gain limiting networks are
good practice.
The idea of using multiple parallel KT88 or 6550
isn't new for high power.
There was a design described in full in a 1957 edition of Wireless
World, which easily tested at 400 watts with 10 x KT88.
All the parts were mounted on a piece of 3/4" plywood,
about 24" x 9", breadboard style. Class A % of the power was
substantial.
Probable use was for a stadium, theatre PA.
Poor struggling musos could never afford such gear, and all the speakers
that went with the amp, and the van to carry it all.
There were 10 ohm resistors to each cathode of the KT88, with a meter which
could be switched
to each 10 ohms to check the bias currents.
The tube idle power dissipation was kept low, and to allow for
uneven bias drift; such amps often have only one fixed bias voltage,
and one has to allow for one or more tube's idle current to
mysteriously escalate during its life.
Nevertheless, the tests of the 1957 amp showed it could sustain
the use of lower load values briefly, and that it was capable of
well over 500 watts.
I believe the prudent designers then would never have considered the use of only
6 x 6550 to do the job.
It'd be like flogging good men to death.
Patrick Turner.
Rich Koerner
lbrt...@aol.com wrote:
>
> Rich Koerner <ri...@timeelect.com> wrote in message news:<40369CAB...@timeelect.com>...
>
> > The 6550WE is NO GE-6550A. It's not even close!!!!!!!!
> >
> > Sonically, or electrically.
>
> Pls clarify, Rich - R U saying that it doesn't dissipate well enough
> under full load?
They don't give high output yield no the loads.
At low frequency, a sine wave is not a good looking sine wave, when the GE yields one.
The screens are not as hardy as the GE's.
Their service life for high power yields is short when compared to the GE.
> If so, what specific failures have you noted or had reported - i.e.
> screen toasted or etc.?
You can't stick a 6550 that is from off shore into everything you can stick a GE 6550A.
You will have to make changes so you don't toast the screens.
In low demanding unit they are OK.
A Leslie amp will not hurt them.
They may live in an SVT for a long period of time, all the while the power output is
slowly going down.
The low end punch on the B and E strings of the bass is getting flabby sounding, and you
may think you have a speaker problem going on.
It's one thing for the tubes to LIVE through the task, and another to HOLD UP high
performance yield, in performing the task.
GE's, hold a high level of performance for a LONG time.
I've NEVER had an imported 6550's give the 435 watts out from a 400-PS.
I slap in a set of GE's, and it's there at 50 Hz.
What does that tell you!!!!!!!!!!!!!!!!!!!!
Simple, ain't it.
> This wld be valuable to know, as well as the
> conditions under which there was a failure, if available.
Look, when someone comes in with an SVT or a 400-PS in the shop, there is a reason WHY,
they own them in the first place.
Magnavox SVT's with GE's do what they do. And, the owner WANTS that at all cost!!!!!
So, I slap in a set of say WE's. I get a call a few months later from the owner, and he
says, I think there is something going on with the amp, it seems to be getting weaker.
The punch in the low end is soft now.
Like the speakers are getting loose.
I slap the thing on the bench, and the output is now lower than were we started, and the
sine wave at low freq. is not so good looking.
Slap in a set of GE's, and the smile on his face says it all!!!!!!!!!!!!!!!!!!!
So, the WE's still work!!!!!!
They don't blow up the amp!!!!!!
So, I guess you can say there is no failure, except..... they just don't live up to the
performance characteristics, and give the service life of the GE-6550A!!!!!!!!!!!!!!!
THAT, is their failure!!!!!!!!
> Yes we know the amp.
>
> Electrically, it would be a stretch to make a distinction; unless the
> mfgr is fraudulent or really lax, a spec is a spec..."not even close"
> would seem to be a rash statement unless some mfgr's version sucketh
> in specific, doccumented ways.
>
> But it was/is not uncommon for some to run them above their 35w plate
> dis at full power, which our old GE's sometimes tolerate somewhat (and
> sometimes didn't or won't, as well).
Well, I've run GE-6550A's at way more than 35w.
More than 50w with out protest.
> None of us hv seen it all, in my case hv yet to see a crappy 6550 that
> wasn't oriental.
My standard for a yardstick IS the 400-PS. Because, the yardstick for the GE-6550A, was
the 400-PS.
That is how the history went.
So, re-writing history to favor the imports, is what is going on here!!!!!!
Patrick Turner
Don wrote:
I enjoyed Cold Mountain, and Lost in Translation, although in the latter case
it was entirely improbable in real life that the younger female lead wouldn't have
bonked
the older lead man, instead of him bonking the singer in the bar closer to his own
age.
America does try to be responsible about where it leads its folks on morals,
and fornication, but there is much hypocrisy......
But nearly all young sheilas of 20 something think its entirely
repugnant to bonk someone twice their age, unless he's stinking rich or famous,
when indeed there are all manner of younger cool dudes,
dateless and desperate to plug in and discard
when the itch needs a scratch.
They never spell it out like this.....
If I walk into a bar, I am Mr Invisible, and I know who the sheilas are watching,
and it ain't me. Used to be me, but not any more.....
And if I started singing folks songs they'd call the police.....
Patrick Turner.
JTM50
totally class A, but more class A than nearly all other amps in the output
stages."
This is called Class A/B1.
Just cause a tube conducts for 360 degrees when it's delivering some amount
less than full power (below the onset of clipping) doesn't mean that it's
operating as Class A at that point.
Lloyd
in article 40393BB5...@turneraudio.com.au, Patrick Turner at
in...@turneraudio.com.au wrote on 2/22/04 3:31 PM:
WakyAmps
>
>
> Miles O'Neal wrote:
>
>> Patrick Turner responded to WakyAmps, who said:
Actually, it was Miles who said... but I've a few questions of
my own.
[humongous snip]
Not sure we're all speaking the same language here ('least I'm
sure as hell not...)
In my dictionary[1], a push-pull amp biased class B has one
output tube in cutoff when the other is conducting. Class A has
both tubes conducting for the entire waveform. Class AB1 has
each tube conducting for somewhat more than half of each cycle,
though the outputs still alternate between cutoff[2].
I think we'll all agree that an AC-30 runs the bejeezus out of
its outputs. However, please explain to me, for a P-P AB1
biased amp, the difference between the "Class A watts" and the
"Class B watts". I don't think I've ever seen those terms used
in that context before.
Are you saying that an AB1 amp where the outputs conduct for,
say, 80% of the signal has more "class A watts" than an amp
where the outputs conduct for 70% of the signal? The latter, of
course, having more "class B watts"?
Just tryin' to understand yer post.
[1] Which I understand may only apply to my very skewed view of
the world, hence the question
[2] and, to be anal, with no grid current -- otherwise it'd be
AB2.
Rich Koerner
to...@nospamprepair.com wrote:
>
> I notice nobody uttered as much as a word about the (formerly Svetlana) now
> Winged C 6550C How come?.
To date, I have not used an of the 6550 flying "C" tubes.
I have no opinion at the moment.
> We use plenty of these in repairs and lot's in
> SVT's with very good results. They aren't GE's or Tung Sol's either but they
> hold up well over time and sound pretty damn good. My 2c
But, it's still substandard performance compared to a good quality GE-6550A.
Patrick Turner
JTM50 wrote:
> From Patrick Turner below: "because they are substantially class A. Not
> totally class A, but more class A than nearly all other amps in the output
> stages."
>
> This is called Class A/B1.
> Just cause a tube conducts for 360 degrees when it's delivering some amount
> less than full power (below the onset of clipping) doesn't mean that it's
> operating as Class A at that point.
In the land of hi-fi amps, class A means that the power input
increases not more than 10% when clipping is reached into the rated class A load.
each of the tubes conducts for 360 degrees of a cycle,
but distortion *currents* do not have more than about 5% 2H in each tube.
Most pentode/tetrode guitar amps are mostly class B amps, with a small % of their
power
in class A. The tube currents in each amp cut right off, and the
distortion currents in each tube contain far more than 5% 2H.
The power input to the output stage increases dramatically, perhaps 100%
when full power in a low bias current AB amp is reached.
Class AB triode amps have much less sharp current cut off,
but still have more than 5% Dn in the tube currents at full power, and as such are
not class A.
A triode's anode voltage rises when that 1/2 of the OPT
primary swings high due to the other side swinging low by a tube being turned on.
The tube turning off is having rising voltage applied to its anode.
This rise in voltage tends to attract electrons, and the tube tries to
conduct more despite the negative going grid voltage.
In triodes, both the grid voltage and anode voltage have an effect on the
electron stream, but in pentodes or beam tetrodes, the
effect the anode voltage has on its own supply of current is
much reduced due to the effect of a fixed screen voltage,
which screens off the electrostatic effect of the anode upon the electron stream
from the cathode.
If you place a 10 ohm R in series from cathode to 0V in the output tubes of a PP
amp,
and examine the voltage at the 10 ohm R, on a CRO, all is revealed about tube
currents.
Patrick Turner.
JTM50
class B amps, with a small % of their power in class A."
I have never seen such a statement in any EE book?
Are you saying that the tube in an A/B or B Class of operation can conduct
for 360 degrees when the power is low? This can be true, however,
What the amp does at less than full power (onset of clipping) has no bearing
on it's Class of operation.
Lloyd
in article 40395E20...@turneraudio.com.au, Patrick Turner at
in...@turneraudio.com.au wrote on 2/22/04 5:57 PM:
Miles O'Neal
> Miles O'Neal wrote:
>> Now this doesn't make any sense at all. In Class A, full tilt isn't
>> different enough from idle to make any difference.
>
> The input power to the 4 x EL84 is around 48 watts. In an ideal class A
> amp, a max of 24 watts in class A is available. But usually, class A max
> efficiency is about 40%, so expect about 20 watts of class A from 4 x
> EL84
Not quite. In a SE Class A amp, you typically
get just under 50%, but 45% is very easy to get.
And Push-pull Class A gets you just a little
better than double what you'd get with an equiv-
alent SE design design of one tube, so you run
right about 50%.
> ...with a few extra AB watts to make it to about 30 at onset of
> clipping. Such operation is substantially class A.
This is where you are wrong. An amp is biased
for one *and only one* class of operation under
its normal operating conditions. It's not Class
A until blah blah blah, despite what some techs
like to say.
Now a Class AB amp will operate similarly to a
Class A amp until the signal starts reaching
cutoff, but that doesn't mean the amp is Class
A until that point. If a PP amp is biased so
that you ever reach cutoff before clipping,
it's not Class A.
[snip]
> The Fender I fixed last week got 21 watts AB1 from 6V6, with 450v supply.
> BIG voltage swing, low current swing, and mainly class B operation. The
> cut off behaviour of tubes is such that the crossover distortion of such
> amps is not entirely awful, certainly not in a guitar amp, where
> distortions are prized, and there is no such thing as really clean
> operation, because it sounds so plain dull and boring.
Well, that's purely a matter of taste. Some
people like clean sounds (many jazz players,
and even for certain kinds of rock). Eric
Johnson, for instance, does some clean stuff
that sounds absolutely *amazing* through his
amps - and they;re all tube.
> One is forced to allow some harmonic distortions, principally 3H, and then
> boost the hell out of all the treble, add some reverb, and maybe it sounds
> well.
If that's what you like, great. But don't
confuse your taste with engineering principles,
OK? 8^P
> Most guitar amps are PP mainly class B in their output stages.
Wrong! Most of them are Class AB, not Class B.
>... Very few
> *pure* class A PP output stages are ever used, and *extremely* few single
> ended class A output stages.
The former is obviosuly correct, but
as to the latter ... there are more and
more of these every day.
> But all the input stages are nearly all SE
> stages using 12AX7, so much of the warmth comes from the SE triode input
> stages which are over driven a bit, and the distortion happens to be
> musically appealing,...
A lot of folks disagree, preferring the sound
of power tube distortion, keeping the preamps
as clean as possible. Again, that's a matter
of taste.
[more snippage - you make *me* look unverbose!]
>> While this is true, some of the tubes made back in the far exceeded
>> their published specs, and hence are worth far more than the common
>> tubes of today, to some people. If it'll last five times as long when
>> being punished, it's worth at least five times the price - more if you
>> calculate the lower likelihood of failure during a gig.
>
> But none of the tubes I have seen will take 5 times the power dissipation
> of an average spec tube. There is *no* 6550 with an anode diss rating of
> 200 watts, and nealry all turn red at just over 45 watts, and then its
> time for prayer, or to reach for the off switch.
And who said they would take that? I haven't
seen anyone talking about a 600W Class A SVT!
>> > In this case, its better to err on the load value by choosing a value
>> > too high, rather than too low!
>>
>> Why not try your friend's PA head into, say, 64 ohms at full blast and
>> let us know how that goes?
>
> If you have a 400 watt amp capable of 400 watts into 64 ohms,
That's not the point. You were talking about how
bad it was to run an 8 ohm amp into 1 ohm or less,
and claimed lower impedances were worse than high.
So I just went up the same amount you went down
(8->4->2->1 vs 8->16->32->64). I can guarantee
that if you try that load, your tube amp will fry,
fry, fry. The closer you get to an open load, the
worse off a tube amp is. It's the opposite for
transformerless transistor output amps - there you
want to avoid getting close to a short at all costs.
We've been over this many times in AGA.
[snip]
> So, I would never recommend that anyone use a 64 ohm load with a
> pentode/tetrode amp which was designed for 8 ohms. 16 ohms would be OK
> though, but 4 ohms could be deadly.
Again, you have it backwards. If you look
carefully, most amps with speaker jacks have
a shorting jack. If a lower load was bad
and a higher load good, they would not do
this!
...
> Nevertheless, the tests of the 1957 amp showed it could sustain the use of
> lower load values briefly, and that it was capable of well over 500 watts.
>
> I believe the prudent designers then would never have considered the use
> of only
>
> 6 x 6550 to do the job.
I dunno, for PA it might work. Check out Rich Koerner's
pages on the Fender PS400 bass amp. It also used six of
the GE 6550As, IIRC, for 400W of bass. You have to know
what you;re doing with it, but apparently it works.
Patrick Turner
WakyAmps wrote:
> Patrick Turner <in...@turneraudio.com.au> wrote in
> news:40393BB5...@turneraudio.com.au:
>
> >
> >
> > Miles O'Neal wrote:
> >
> >> Patrick Turner responded to WakyAmps, who said:
>
> Actually, it was Miles who said... but I've a few questions of
> my own.
>
> [humongous snip]
>
> Not sure we're all speaking the same language here ('least I'm
> sure as hell not...)
>
> In my dictionary[1], a push-pull amp biased class B has one
> output tube in cutoff when the other is conducting. Class A has
> both tubes conducting for the entire waveform. Class AB1 has
> each tube conducting for somewhat more than half of each cycle,
> though the outputs still alternate between cutoff[2].
>
> I think we'll all agree that an AC-30 runs the bejeezus out of
> its outputs. However, please explain to me, for a P-P AB1
> biased amp, the difference between the "Class A watts" and the
> "Class B watts". I don't think I've ever seen those terms used
> in that context before.
Most guitar amps are class AB1 amps.
This means that for say the first 5 watts, both output tubes
operate with low distortion content in their currents,
and are like two single ended tubes but working together to change the
opt primary
voltage in a balanced manner.
Beyond the 5 watt power level, one of the tubes recieves a large enough
negative going grid voltage to cut the current flow right off.
The other tube grid is getting a positive going voltage to turn on the
tube
current much more, and so power is produced by one tube only
during the crests and troughs of the sine wave. Only the zero crossing
part of the sine wave power cycle is where both tubes mutually
contribute power.
So over 5 watts in the above typical amp, the power can be said to be
classB.
But viewed as a whole, during a maximum level sine wave,
the operation is class AB.
AB1 indicates tubes are not driven to draw grid current, AB2 means
the amp is driven hard to make the grids draw grid current.
Once upon a time, nearly all makers used a much lower screen voltage
than today, where the trend is to have both anode and screen supplies
quite high, say both at 450v.
Originally, 6550 and 6L6 and 807 were configured with screens
set at 300v max, and then anode voltages could be much higher.
Even 807 were run with 600v at the anode, and 300v for screens,
and 80 watts class AB2 were available.
The lower the screen voltage, the lower the grid1 bias voltage,
and the lower the AB1 power output ability into a low value RL.
So to get more anode swing, the grid1 is damn well forced to swing
more, and above 0V ie, positively, when it conducts current,
so a cathode follower drive stage is required.
The result is that the screen currents overall tend to stay low, and the
screen dissipation
tends to stay well within the operational ratings, and the tube lives to
a ripe old age,
and it don't die screaming.
>
> Are you saying that an AB1 amp where the outputs conduct for,
> say, 80% of the signal has more "class A watts" than an amp
> where the outputs conduct for 70% of the signal? The latter, of
> course, having more "class B watts"?
Indeed.
Most guitar amps have maybe 5 watts of what is class A power,
and the remaining 55 watts are class B.
That's a total of 60 watts of class AB.
>
>
> Just tryin' to understand yer post.
>
> [1] Which I understand may only apply to my very skewed view of
> the world, hence the question
Transistor amps' output transistors are almost all class B.
only milliwatts of class A. the top half of 1/2 the sine wave is
powered by one device, the bottom 1/2 by the other device.
Its possible to set them up with a much higher idle current,
so each swings its current +/- either side of the idle current,
which is class A, but almost nobody does, because
it wastes electicity to keep that much heat, ie, idle power,
which is voltage across the devices x current thtough the devices.
The same issues exist with tubes, or mosfets.
>
>
> [2] and, to be anal, with no grid current -- otherwise it'd be
> AB2.
Indeed.
I have an old 1957 Brimar tube data book,
and in the back, there are all these typical old circuits for tube gear,
including an 80 watt class AB2 amp for 807.
They didn't use high screen voltages.
They drove the grids harder instead.
Since that time, versions of 6L6, 6V6 have been made
to cope with higher screen currents.
I am not sure about the 6550.
Much criticism has been levelled at the current productions'
tendency to fragile screens; I like to run the screens at 300v,
and have about 500v on the anode unless its triode, where
both have about 450v, or UL where its up to 500v.
Triode or UL operation limits the max value of voltage applied
to about 500v.
But beam tetrode operation allows the screen to be fixed
at a lower voltage than the anode supply, hence the 80 watt case using
807.
The idea of the lower Screen voltage means the screen voltage x screen
current
remains low, so the screens remain cool, and don't run red hot.
After they turn orange, the thin wires bend and deform, and
the alignment of the screen wires with the grid 1 wires becomes
wrong, and the tube's linearity and max power ability is seriously
compromised.
If you want to know more about tubes, the read
the Radiotron Designer's Handbook, 4th Ed, 1955.
There isn't much about 6550, KT88, EL34, EL84,
but a lot of useful info about 807, 6V6, KT66 and 6L6,
which were the main power tubes at that time.
Lots of theory.
There is rather more to learn than can be said in a few emails......
Patrick Turner.
Patrick Turner
JTM50 wrote:
> Patrick Turner wrote below: "Most pentode/tetrode guitar amps are mostly
> class B amps, with a small % of their power in class A."
>
> I have never seen such a statement in any EE book?
And you probably won't ever.
But one has to describe the distinctions between class A and class AB somehow.
>
> Are you saying that the tube in an A/B or B Class of operation can conduct
> for 360 degrees when the power is low? This can be true, however,
> What the amp does at less than full power (onset of clipping) has no bearing
> on it's Class of operation.
Perhaps if you read my other posts where I try to define
what is class A, B, and AB, et all, you may get the picture.
If only I could show you the cathode current wave forms on my CRO!
all would become clear in 10 seconds. Its simple what happens.
Patrick Turner.
>
>
> Lloyd
Steve Eaton
"Don" <TAKE-OUT...@comcast.net> wrote in message
news:LWVZb.96590$jk2.454775@attbi_s53...
"Songcatcher" is a great movie with excellent renditions of old
Appalachian/Scots-Irish
songs throughout it.
"Brother ,Where are art Thou" is a bit goofier, but in that cool Coen Bros.
kind of goofy,
(The Big Lebowski style) but it is also loaded with good acoustic music done
very well.
Lotsa "old-timey" music:-)
Steve Eaton
"Miles O'Neal" <m...@rru.com> wrote in message
news:pan.2004.02.22....@rru.com...
> Patrick Turner responded to WakyAmps, who said:
>
> ...
> >> Remember, Rich claims that the GE and Sov "aren't even close" sonically
> >> or electrically. Maybe so in his tweaked 400PS and to his ears and
> >> playing style; there may not be as strong a case in the OP's RI-SVT and
> >> to the OP's ears and style.
> >
> > How anyone can tell much difference between the sound of tubes when the
> > thd is at around 25%, and IMD at around 50% is beyond me.
>
> Just curios - are you a musician? Do you care about
> tone? Do you consider your ears good? Because the
> sonic differences in tubes are ell documented. My
> wife and kids, none of whom play guitar (Josiah keeps
> saying he wants to, but never practices much) can hear
> these differences, and they aren't tube freaks by any
> stretch of the imagination!
>
> [Story of 0 ohm tube PA into < 1 ohm bins snipped]
I think that the differences in the tubes are actually a lot more noticible
as the distortion gets higher.
In HiFi or a PA you might not want distortion, so you are running
as clean as you can normally. OTOH perfectly clean guitar as in straight
into a mixing board sounds pretty lifeless and cold, so guitar folks want
that
distortion, and the kind of tubes affect how that distortion sounds greatly.
One may not have the ears or desire to hear that kind of a sound and
be able to tell the difference, but it is a reality.
WakyAmps
news:103isui...@corp.supernews.com:
>
> I think that the differences in the tubes are actually a lot
> more noticible as the distortion gets higher.
> In HiFi or a PA you might not want distortion, so you are
> running as clean as you can normally. OTOH perfectly clean
> guitar as in straight into a mixing board sounds pretty
> lifeless and cold, so guitar folks want that
> distortion, and the kind of tubes affect how that distortion
> sounds greatly.
>
> One may not have the ears or desire to hear that kind of a
> sound and be able to tell the difference, but it is a
> reality.
>
Or, said faster:
Most of us are into production, not reproduction.
JTM50
in...@turneraudio.com.au wrote on 2/22/04 6:44 PM:
>
>
> JTM50 wrote:
>
>> Patrick Turner wrote below: "Most pentode/tetrode guitar amps are mostly
>> class B amps, with a small % of their power in class A."
>>
>> I have never seen such a statement in any EE book?
>
> And you probably won't ever.
> But one has to describe the distinctions between class A and class AB somehow.
>
>>
>> Are you saying that the tube in an A/B or B Class of operation can conduct
>> for 360 degrees when the power is low? This can be true, however,
>> What the amp does at less than full power (onset of clipping) has no bearing
>> on it's Class of operation.
>
> Perhaps if you read my other posts where I try to define
> what is class A, B, and AB, et all, you may get the picture.
Patrick I know what the various amp classes mean. Tell me on what page of
the Radiotrons desiners handbook I can read about percentages of power in
various classes as you have mentioned? I happen to have the 4th edition.
I have been told and (since read) that how much a tube conducts before full
power/onset of clipping has no bearing on determining it's Class of
operation. I may have even read this in the RDHB.
Yes, I know that a Class A/B amp will have the tubes on (and amplifying) all
the way trough the cycle (like Class A does) up to a certain point (of
power delivered). After this point of power output the individual tubes
start conducting less and less as the power increases. This is called Class
A/B.
Lloyd
Fred Nachbaur
JTM50 wrote:
I think the difficulty here is just semantics. In order to give an
classification to a particular real-life amplifier design, the classes
of operation were defined. These relate to overall amplifier performance
parameters, a very important one of which is maximum output power.
You're absolutely right. A Class AB2 amplifier is exactly that, since
one tube is cutoff for part of the cycle (the "AB" part), and
furthermore goes partly into grid conduction during part of the cycle
(the "2" part).
The reason I used this example is that I built such a thing not long
ago, and when documenting it on my website had to find a way of giving
an idea at what power levels the two significant non-linearities entered
(the first being cutoff, the second being grid conduction). I opted for
an approach much like what Patrick uses in explaining this. Below a
certain power level, this Class AB2 amplifier actually *behaves* like a
Class A amp. Above that, but below grid conduction, it *behaves* like a
Class AB1 amp. Beyond that, to the hard-clipping point, it actually
behaves like what it is - a Class AB2 amplifier.
If you're curious, the specs are here:
http://www.dogstar.dantimax.dk/tubestuf/dz-perf.htm
Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+
Patrick Turner
Miles O'Neal wrote:
> On Mon, 23 Feb 2004 10:31:02 +1100, Patrick Turner wrote:
> > Miles O'Neal wrote:
>
> >> Now this doesn't make any sense at all. In Class A, full tilt isn't
> >> different enough from idle to make any difference.
> >
> > The input power to the 4 x EL84 is around 48 watts. In an ideal class A
> > amp, a max of 24 watts in class A is available. But usually, class A max
> > efficiency is about 40%, so expect about 20 watts of class A from 4 x
> > EL84
>
> Not quite. In a SE Class A amp, you typically
> get just under 50%, but 45% is very easy to get.
45% is very optimistic, and represents the practical
limit for class A efficiency.
Most tetrode/pentode amps are 35%.
>
> And Push-pull Class A gets you just a little
> better than double what you'd get with an equiv-
> alent SE design design of one tube, so you run
> right about 50%.
Very seldom.
The amp doing 50% plate efficiency is usually
operating with considerable class AB.
the max efficiency of class B with tubes is around 66% only.
>
>
> > ...with a few extra AB watts to make it to about 30 at onset of
> > clipping. Such operation is substantially class A.
>
> This is where you are wrong. An amp is biased
> for one *and only one* class of operation under
> its normal operating conditions.
No, most amps with enough bias current will operate
as pure class A amps with an appropriate minumum load to alow this to occur.
Below this load, they are class AB, and above that min load, the power is all
class A
> It's not Class
> A until blah blah blah, despite what some techs
> like to say.
>
> Now a Class AB amp will operate similarly to a
> Class A amp until the signal starts reaching
> cutoff, but that doesn't mean the amp is Class
> A until that point.
I think your'e the one who has it wrong.
One could have a class AB amp, each tube is operating in class
A at low voltage/current swings.
One can prove this easily. Set up a PP amp with 6L6 and Ea = 400v,
and bias at 30 mA.
use about a 5k a-a load.
measure the current into the CT on the OPT.
there is a region of operation where the current input stays constant,
hence the power input is constant, and the amp *must* be working in class A.
As soon as one tube begins to cut off while the other carries on,
its class AB, and the power input starts to rise, indicating class AB.
> If a PP amp is biased so
> that you ever reach cutoff before clipping,
> it's not Class A.
But the cut off isn't linear in many tubes, and in amps which are
regarded as class A, there is still a slight increase in power input
near clipping, because the current cut off in one tube is less than the current
increase in the other. If the wave forms of the cathode currents are examined
its plain to see that in a class A amp, each output tube has
quite a lot of 2H distortion current, but not actual complete current cut off.
> [snip]
>
> > The Fender I fixed last week got 21 watts AB1 from 6V6, with 450v supply.
> > BIG voltage swing, low current swing, and mainly class B operation. The
> > cut off behaviour of tubes is such that the crossover distortion of such
> > amps is not entirely awful, certainly not in a guitar amp, where
> > distortions are prized, and there is no such thing as really clean
> > operation, because it sounds so plain dull and boring.
>
> Well, that's purely a matter of taste. Some
> people like clean sounds (many jazz players,
> and even for certain kinds of rock). Eric
> Johnson, for instance, does some clean stuff
> that sounds absolutely *amazing* through his
> amps - and they;re all tube.
Its true what you say about taste. But I have never met a muso
who prefers solid state, or perfectly linear tube amps.
>
> > One is forced to allow some harmonic distortions, principally 3H, and then
> > boost the hell out of all the treble, add some reverb, and maybe it sounds
> > well.
>
> If that's what you like, great. But don't
> confuse your taste with engineering principles,
> OK? 8^P
I wasn't.
The preferences of musos vary considerably.
>
>
> > Most guitar amps are PP mainly class B in their output stages.
>
> Wrong! Most of them are Class AB, not Class B.
I think you misunderstand.
Most guitar amps display full cut off of the tube *current* for most of the
cycle at clipping with a sine wave.
Don't think about the output signal voltage; that will be substantially linear
and clean with a largely class B amp.
Think in terms of tube currents.
The class AB amp relies on the combining of two tubes non linear current flows
to sum in an opt to make a linear outcome.
Even in a class A amp, the same thing occurs, but not as badly as a
low bias current, high supply voltaged amp.
With 2 x 6v6, the maximum pure class A available regardless of
loadings is about 40% max of the 24 watts max idle dissipation,
so 9.6 watts is all you get.
If the amp is set up for class AB, the AB power max is about 21 watts
of which 5 could be class A, and the remaining 16 is B, because
after 5 watts, the tubes start to cut off during the cycle.
Connect a CRO to a cathode resistor, and you will see what happens.
>
>
> >... Very few
> > *pure* class A PP output stages are ever used, and *extremely* few single
> > ended class A output stages.
>
> The former is obviosuly correct, but
> as to the latter ... there are more and
> more of these every day.
Not much use of SE musicians amps.
The SE amp is a gutless wonder to many musos.
2 x 6550 might be set up to reliabably idle at
400v x 80 mA = 32 watts, so 64 watts for the pair..
At one optimal load value, the plate efficiency is 40% max,
so you get 26 watts of class A.
The same two tube give up to 75 watts easily in PP.
Much more bang for the buck from a muso's point of view,
and 99% of musos are dirt poor, 1% have talent, luck,
and get the break....
But wish good luck to any musos using SE amps.
In hi-fi amps, good SE amps rule, because its possible to
obtain subjectively better fidelity, and the first 5 watts are all important.
and most serious hi-fi enthusiasts just ain't deaf, and
10 watts covers 95% of what they listen to.
>
>
> > But all the input stages are nearly all SE
> > stages using 12AX7, so much of the warmth comes from the SE triode input
> > stages which are over driven a bit, and the distortion happens to be
> > musically appealing,...
>
> A lot of folks disagree, preferring the sound
> of power tube distortion, keeping the preamps
> as clean as possible. Again, that's a matter
> of taste.
Each unto their own....
>
>
> [more snippage - you make *me* look unverbose!]
>
> >> While this is true, some of the tubes made back in the far exceeded
> >> their published specs, and hence are worth far more than the common
> >> tubes of today, to some people. If it'll last five times as long when
> >> being punished, it's worth at least five times the price - more if you
> >> calculate the lower likelihood of failure during a gig.
> >
> > But none of the tubes I have seen will take 5 times the power dissipation
> > of an average spec tube. There is *no* 6550 with an anode diss rating of
> > 200 watts, and nealry all turn red at just over 45 watts, and then its
> > time for prayer, or to reach for the off switch.
>
> And who said they would take that? I haven't
> seen anyone talking about a 600W Class A SVT!
Well if some of the hype about some of the sturdier 6550 brands
are to believed, you'd think there is some magical quality,
some special ability for the tube to exceed the ratings,
but there is no magic in the ratings.
Perhaps the cathode emisions under stress do vary over time
somewhat earlier with russian tubes.
I have not noticed falling emissions with russian tubes,
but then we havn't had time to evaluate this.
Maybe in 30 years, some grey haired old bugger
will hark back to his youth in 2004, and try to tell
folks that 2004 tubes are so much better than 2034 tubes.
There will be only 3 samples left in the world of mint GE 6550 in 2034,
and arguments will rage that perhaps they are chinese fakes....
>
>
> >> > In this case, its better to err on the load value by choosing a value
> >> > too high, rather than too low!
> >>
> >> Why not try your friend's PA head into, say, 64 ohms at full blast and
> >> let us know how that goes?
> >
> > If you have a 400 watt amp capable of 400 watts into 64 ohms,
>
> That's not the point. You were talking about how
> bad it was to run an 8 ohm amp into 1 ohm or less,
> and claimed lower impedances were worse than high.
> So I just went up the same amount you went down
> (8->4->2->1 vs 8->16->32->64). I can guarantee
> that if you try that load, your tube amp will fry,
> fry, fry. The closer you get to an open load, the
> worse off a tube amp is.
Any tube amp should be able to be used without a load
up to when the voltage swing reaches the peak value of the supply voltage.
To make sure the swing is limited to stop arcing.
diodes from anodes to 0V can be added, as seen in the schematic at
http://www.turneraudio.com.au/htmlwebpgs02/schem100ulabmono.htm
There are three diodes in series to limit the negative swing of the
anode voltages. Without a load, the OPT
voltage swing can be 3 times the supply voltage.
The amp *will not* fry without a load, because there is
very small current change and hence no more power liberated as heat
in the tubes beyond the idle power dissipation.
The only reason preventing full output signal voltages with no load in tube amps
is appalling design methods, ie, bean counters, ie, the humans failing to
take enough responsibility for their constructions.
> It's the opposite for
> transformerless transistor output amps - there you
> want to avoid getting close to a short at all costs.
> We've been over this many times in AGA.
Shorts in OTLs and transistor amps are deadly, I agree,
but just as deadly in a transformer coupled tube amp, except the tubes take
longer to
over heat and melt, than a transistor, with its tiny little chip
inside its case.
And its hoped that the failing tube doesn't make 1/2 the opt primary go open.
>
>
> [snip]
>
> > So, I would never recommend that anyone use a 64 ohm load with a
> > pentode/tetrode amp which was designed for 8 ohms. 16 ohms would be OK
> > though, but 4 ohms could be deadly.
>
> Again, you have it backwards. If you look
> carefully, most amps with speaker jacks have
> a shorting jack. If a lower load was bad
> and a higher load good, they would not do
> this!
The shorting jack is there to prevent the amp from ever seeing an open circuit,
or no load, when it may indeed misbehave by oscillation and die from
its poor design.
Its very unlikely anyone will use the amp with no speaker connected.
Nobody likes playing music at a gig in silence.
All my amps can be used with or without a load, no worries.
accidental signals taken up to clipping with no load does *zero* damage.
> ...
> > Nevertheless, the tests of the 1957 amp showed it could sustain the use of
> > lower load values briefly, and that it was capable of well over 500 watts.
> >
> > I believe the prudent designers then would never have considered the use
> > of only
> >
> > 6 x 6550 to do the job.
>
> I dunno, for PA it might work. Check out Rich Koerner's
> pages on the Fender PS400 bass amp. It also used six of
> the GE 6550As, IIRC, for 400W of bass. You have to know
> what you;re doing with it, but apparently it works.
I have no reason to ever suggest that what Fender does with bass amps
doesn't work.
The same amp would handle operating as a PA amp.
But 6 tubes for 400 watts is too few tubes, imho.
I think Fender should have used 10.
12 is a nicer number....
Marshall use 4 x EL34 to get 100 watts,
so for 400 watts, 16 x EL34 should be used.
With 12 tubes in my amps, I get away with separate RC cathode bias
for each tube, in my case with 15 watt x 500 ohms with 1,000 uF per tube
cathode.
All the worry about biasing 12 tubes properly does not exist,
since auto bias sets itself very reliably.
The tubes get it easy in my amps, and i hope they last, and last, and last......
Patrick Turner
to...@nospamprepair.com
currents from zero excite signal to 30W output. I could go find those and
post here if anybody is interested. I have since obtained an AC current
probe for my scope and as soon as I figure out how to work the damn thing I
will observe further. If I follow this thread correctly -oh by the way, I
LIKE WINGED C (formerly Svetlana) 6550C's FOR THE SVT. where was I? , if I
follow this discussion correctly there is some interest in properties of the
AC30 and/or the subtleties in bias classification.
I for one am not the expert on how to determine in a comprehensive way
whether the AC30 is Class A or possibly what is known as A2? or as some like
to say "hot AB1" though I am armed with a mighty library and some general
observations on this particular amp so I would like to throw in my 2c if
it's worth that much to you folks:
Though the AC30 may not be purely Class A it's operating characteristic is
so far removed from any other AB1 guitar amp I have ever seen (except for a
few antiques) that I would by my own definition have to say that it is at
least in a class of it's own - whatever class that is! By observing DC plate
input power -vs- plate output power alone, it behaves quite differently from
any other guitar amp I know of. The short story on my measurements is that
from zero signal to 30W output there is a change in DC plate current of
roughly 3mA per tube - it barely flinches. I certainly don't know of any
other Class AB1 amp that works like that.
Todd
"Fred Nachbaur" <fnac...@netscape.net> wrote in message
news:Khg_b.36557$n17.26746@clgrps13...
Rich Koerner
Patrick Turner wrote:
<snip of Rich's stuff>
> It is with interest I read your ideas about providing music
> with feeling, rather than with false edgy sounding fake bass.
>
> I also see the Fender 400 watt amp you refer to has only 6 x 6550
> tubes to make the 400 watts, which means 133 watts per pair of 6550,
> which is rather a lot of stress on the tubes, regardless of the brand of tubes used.
First, understand where the 400-PS and GE-6550A came from originally!!!!
Those GE's were made to work in the only test bed of any worth!!!!!!
I had to do testing of the 6550A's that GE had sent to me for testing in the 400's.
It was my feedback to Harry Storm, and Chris McCool on those ENGINEERING SAMPLES, that
tweaked the tube to what it became.
One other little known fact about the GE is the function of the glass used for it, is a
one of a kind with respect to it heat transfer characteristics.
Ever wonder WHY, there is no cooling fan in a 400-PS!!!!!!!
The reason,.... because by the design of the GE-6550A and the make up of the glass, it
doesn't REQUIRE any extra cooling, for that level of performance found in the
400-PS!!!!!!!
> When such an amp is is pushed into over drive one would think
> that screen currents and grid currents could be rather high,
> and the danger of tube damage would be ever present,
> especially if someone connects too many speakers accidentally.
That is true of the imports!!!!!!!
And that, is THEIR problem!!!!!!
> Ever thought of using a dozen 6550 to do the job?
WHY, with the GE-6550A, runing AB, they can in a modified 400 yield 560 watts R.M.S. @ 50
Hz.
Much higher outputs at higher frequencies, is also normal from the 400's.
Hell, a stock modified will approach 190 watts for each of the three test loads @100 Hz.
The estimated total,... 570 watts R.M.S.
> This reduces the power per pair to a more survivable 66 watt.
> Audio Research use 16 x 6550 for their Reference 600,
> and that 75 watts per pair, same as a humble McIntosh.
Hey, I'm not talking audiophile gear here!!!!!
I want to reproduce the sound of my Jazz Bass, and shake your gut doing it!!!!!
I want to make the bottels dance in the bar, and you can't hear what's doing it.
But you sure as hell can feel what's doing it.
> See http://www.turneraudio.com.au/htmlwebpgs02/300monobloc.htm
> to see a sample.
Nice glass bill when it time to replace 'em all.
But, if you started out with a full set of GE-6550A's, You can most likely figure you
saved your great grand kids a pile of bucks, so they don't need to replace any tubes yet.
Life extention is not measured by just one test case.
Parallel that current tube, with that of the GE, and now see which lives the longest.
So, no matter which way you want to spin the 6550 spin for those from off shore, the GE's
are the shit.
> My amps make about 200 watts of class A, and its all very relaxed
> and the idea is to have limitless headroom for a hifi situation,
> where effortless and distortion free sound is sought.
Yeah, and class A don't beat the shit out of the screens like AB ultra linear does.
There is another example where you don't go sticking the wanna be 6550's straight, in
where the GE's go.
Why, because they ain't the SAME!!!!!
> In one of my 8585 hifi amps, I used 8 x jan GE6550, nos, green lettering.
> They were about twice the price I pay now for EH6550.
> I don't know wherther there was anything really special about them.
> After 7 years of on -off use in a hifi situation, they all became prone to
> grid current even at idle, and some of the grids going a volt or two positive.
> Then I reduced the bias resistors to 100k, and they held their bias better.
Well then, to exactly who's family of 6550 curves was that amp designed.
The GE's, or the wanna be 6550's.
I KNOW, they ain't the same, so which way did the designing go here.
> The client had me replace all the tubes with EH 6550,
> and he said there was a big improvement in the soundstage,
> which seemed to have depth, not only width, as before with GE,
> then he said the dynamics and detail were improved.
Like the Tungsol is to the GE, so are other tubes with the same numbers on the glass.
The tube's curves are different, their windows of operation is different, their loading
windows to the OT's are different, and the OT loading designs are different manufacturer
to manufacturer.
So, just where does this all line up for the GE. For the EH.
Get the picture.
With respect to your client:
What is the program material we talking about here.
How long is HIS audio retention good for.
Just what was the length of time between comparisons.
Define his meaning of the words DEPTH and WIDTH.
If that was made with respect to the Sonic Field, that is the biggest crock of shit I've
ever heard!!!!!
Gee, I didn't know that just by changing output tubes, you could IMPACT the hardly heard
anymore 3D sonic field, that truely escapes the clue less engineer/producers of today's
generation
So, this better be a stereo system, and the program material better have that tudio
engineered 3d sonic image, that is very rare in the history of recorded music, for me to
take any of these claims seriously.
Then likewise, Define his meaning of the words DYNAMICS and DETAIL.
Hmmmmmmmm.......................!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
<thinking>
Screw it.
What the hell am I supposed to do with this meaningless babble!!!!!!!!!!
What,.. did we get a freq increase or band width increase here!!!
What's the deal.
You tell me!!!
I ain't got no crystal ball.
Where's the RTA, power, and impedance curves of both conditions!!!!!
> Hifi amps are never subject to severe signal overloads and gross clipping
> with rock musician amps.
OK,.... I guess I just got it!!!!!
Forget what I said one click above.
Your client is all full of crap, and imagined it.
There is NO WAY, a change of output tube can impact the sonic field of STEREO system in
either a well mixed 3D, or the standard BS 2D most ALL of us hear from our everyday
recordings.
Long gone are the days when engineer/producers even had 3D mixing in mind when setting up
the mics in the studio!!!!!!!
So, to me, his words are meaningless!!!!!!!!
As meaningless as the tall tails told by those who've had sex with aliens, and the baby
produced has super hearing for things not of the real world.
> But they are left running for hours on end, day after day,
> with a substantial bias current to allow lots of class A.
> I guess the tubes wear out for different reasons in the
> music amp versus the hi-fi amp.
Correct!!!!!
Class A is a waste of electricity, to reproduce silence!!!!!!!!!!!
But then, look of all the tube gear of the past that was left on 24/7 in all the labs
across this land where tolerance and calibration had to be held.
Look at all the communications transmitters that required the same.
There are a lot of 24/7 tube examples besides this one.
So, it's the Class A, that kills ya on this one.
So, as an enviornmentally frendly person, I use AB only for my audio needs.
But, don't you dare call me a Tree Hugger!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> One of the sweetest music amps I heard was 6V6 PP,
> about 80% UL taps, nearly triode, in class A.
> Another 6V6 in triode drove the output stage via a transformer.
Look, I've had my share of Hifi gear experience through my life time. I also prefer to
follow the laws of mother nature with respect to the natural world around me.
Audiophile books are no substitute for the physics book on the subject, when it comes to
understanding the world around you..
> This amp was one of the few which seemed to have sweetness
> and a sort of natural reverb,
Here we go again!!!!!!!!!!!!!!!!!!!
Who's on first, what's on second, I don't know, third base!!!!!!!!!!!!!!!!!!!!!!!
Natural room reverb, is NOT the product of ANYTHING, that has anything to do with the
amplifier itself!!!!!!!!
Natural room reverb is governed by other things!!!!!!!!!!!!!!!!!
> but without a reverb unit used.
> The owner-builder was a physics lecturer, whose interest off campus was guitar,
> and rocket engines.
And maybe a collection of tin foil hats in the closet too.
> Another client uses Sovtek 6550 in triode in a Marshall head for use
> in his "dark metal" band,
OK, now I know about that stuff.
> and the sound is basically like a continual stream
> of jumbo jets crashing on the pavement in front of you.
There you go again.
Just when I thought we were going to connect, you get weird on me again.
I wouldn't have a clue what the hell the sound of crashing jumbo jets crashing in front of
me would sound like.
Let alone coming from a Marshall in triode with sovtek wanna be 6550's.
Pisssssssssssssssssssssssssssssst!!!!!!!!!!!!!!!!!!!!
Ummmmmmmmmmmmmmm......................!!!!!!!!!!!!!!!!!!!!
Ya wanna hear what I can do with a 400-PS with three full Marshall stacks on it with my
Strat, fuzz face, vox wah, octave down box, etc.... ALL up on TEN, in full Jimi glory
doing my version of the Star Spangled Banner!!!
You think I would come close to what your friend has going on with the Jumbo Jets
thing!!!!!!!!
> Not my cuppa tea, but some folks think its very cool!
> The tubes are either off, or 40 dB over clipping.
> After 4 years, I think he's on his second pair......
> The first pair expired after using too low a load impedance
> when swithed to the 16 ohm setting.
> So when I hear about tubes failing, I wonder first
> about the human element.
No, you have to wonder about the quality of the materials that are actually used in the
tube. The purity of the vacuum of the tube. Then, the degree of vacuum when tipped off.
These are just for starters!!!!!
> Unlike Fender, I fit individual cathode current sensors
> to each output tube so that if any one tube out of so many
> misbehaves, and goes red with too much cathode current,
> the amp is turned off.
Good idea!!!!!!!!!!!!!!!
> That mightn't suit a muso, who might prefer to blow a few tubes rather than stop
> to change to a spare amp between songs, if the fuse hasn't blown.
>
> Patrick Turner
Oh, I see this was cross posted.
That explains things a tad more.
Rich Koerner
"James Angelo Ruggieri, P.E." wrote:
>
> I would guess any tube whose structural elements are rigid enough to
> maintain spacing and does not readily "short" when subject to
> shock/vibration. This can be easily determined by energizing the amp with a
> 100 Watt clear light bulb in series with the line, and with all the tubes
> installed, tapping on the tubes with a rubber handled screwdriver - while
> observing the series line light for changes in luminance.
I think this is a poor substitute for a speaker and an ear.
In high gain instrument amplifiers, my instrument becomes microphonic, and will brighten
the lamp.
Yet, this is a normal condition, and to the train ear, one can learn which microphonics
from what location, are the unwanted ones.
Variation in lamp brightness, yields limited information.
> Changes in the
> light would indicate structurally unstable tube elements - meaning it is
> likely the amp/tubes will short during service. Otherwise, I doubt you would
> be able to discern any quality difference. The SVT is also tough to
> balance - from what I recall, and can be very touchy.
>
> Jim
Regards,
James Angelo Ruggieri, P.E.
The light will brighten as current demand to the amp increases - however, a
light brightening as a result of shock induced to the tube has nothing to do
with sound. It is also doubtful that anyone can discern any differences
among tubes built within specification - even if one's ears are made of
foreskin.
--
JAMES RUGGIERI
"Rich Koerner" <ri...@timeelect.com> wrote in message
news:4039FFE2...@timeelect.com...
James Angelo Ruggieri, P.E.
non-linear with respect to frequency - often intentionally introducing
distortion and harmonics - and this is what sets these amplifiers apart
from one another. On the other hand - and as you have stated, the HiFi
devices are designed for flat reproducibility.
For instance, an old Marshall Major at 400 Hz will output only 20 V,
however, sweep the frequency to 5 KHz and the output will rise to nearly 50
V. Additionally, cadence amps are designed to accommodate a wide variation
of tubes, as well as variations in fixed components, such as resistors.
Often 10 and 20% resistors are used, as well as 10 to 40% frequency
impacting capacitors. This is done to accommodate availability of
components. A Monte Carlo analysis of performance, given the possible
component variations, shows a very wide variation among amplifiers of same
production. That is, there can be no expectation that any two cadence
amplifiers of same production to perform the same. Now whether or not the
differences are sufficient enough to permit detection by the human ear is
another matter.
Jim
--
JAMES RUGGIERI
"Steve Eaton" <steve...@hotmail.com> wrote in message
news:103isui...@corp.supernews.com...
Patrick Turner
Rich Koerner wrote:
> Patrick Turner wrote:
>
> <snip of Rich's stuff>
>
> > It is with interest I read your ideas about providing music
> > with feeling, rather than with false edgy sounding fake bass.
> >
> > I also see the Fender 400 watt amp you refer to has only 6 x 6550
> > tubes to make the 400 watts, which means 133 watts per pair of 6550,
> > which is rather a lot of stress on the tubes, regardless of the brand of tubes used.
>
> First, understand where the 400-PS and GE-6550A came from originally!!!!
>
> Those GE's were made to work in the only test bed of any worth!!!!!!
>
> I had to do testing of the 6550A's that GE had sent to me for testing in the 400's.
>
> It was my feedback to Harry Storm, and Chris McCool on those ENGINEERING SAMPLES, that
> tweaked the tube to what it became.
>
> One other little known fact about the GE is the function of the glass used for it, is a
> one of a kind with respect to it heat transfer characteristics.
>
> Ever wonder WHY, there is no cooling fan in a 400-PS!!!!!!!
>
> The reason,.... because by the design of the GE-6550A and the make up of the glass, it
> doesn't REQUIRE any extra cooling, for that level of performance found in the
> 400-PS!!!!!!!
So at least you are confirming that the tubes *will* be able to run hotter
than other tubes.
My worry is still that the plate temp and screen temp
might get too high for peace of mind.
If one uses say 10 tubes for 400 watts, the heat per tube
is reduced, so no need for special nos versions of 6550.
>
>
> > When such an amp is is pushed into over drive one would think
> > that screen currents and grid currents could be rather high,
> > and the danger of tube damage would be ever present,
> > especially if someone connects too many speakers accidentally.
>
> That is true of the imports!!!!!!!
>
> And that, is THEIR problem!!!!!!
Its anyone's problem when some fool tries to
force tube to work into too low a load.
>
>
> > Ever thought of using a dozen 6550 to do the job?
>
> WHY, with the GE-6550A, runing AB, they can in a modified 400 yield 560 watts R.M.S. @ 50
> Hz.
560 watts for six tubes is 186 watts per pair of tubes, which is absolutely flogging the
bejeesus
out of the tubes, and I would never do this to dwindling supplies
of precious nos tubes of great alleged quality.
560 watts is only 3 dB louder than 280 watts.
>
> Much higher outputs at higher frequencies, is also normal from the 400's.
I can't see how. most good amps have the same power output at 50 Hz as at 1 kHz.
If its a decent amp that is.
>
>
> Hell, a stock modified will approach 190 watts for each of the three test loads @100 Hz.
>
> The estimated total,... 570 watts R.M.S.
>
> > This reduces the power per pair to a more survivable 66 watt.
> > Audio Research use 16 x 6550 for their Reference 600,
> > and that 75 watts per pair, same as a humble McIntosh.
>
> Hey, I'm not talking audiophile gear here!!!!!
Yes, I am aware you are talking bass amps.
Hi-fi amps have a different philosphy behind their design;
linearity and cool running and reliablity, and class A %
are the important factors kept in mind to keep thd levels
20 dB lower than a guitar amp.
So 50 watts per pair of 6550 is about right.
Where 100 watts is required, use 4 tubes, rather than hot up the amp
using tubes.
Its a case of using more engine cylinders to make the ship go faster,
rather than rev the guts out of just two cylinders.
>
> I want to reproduce the sound of my Jazz Bass, and shake your gut doing it!!!!!
I realize all that, and some dudes really think that's all so cool.
But not me. I used to like loud bass, have a joint after ridin over to the gig
on a Harl but I discovered other things since then.....
>
>
> I want to make the bottels dance in the bar, and you can't hear what's doing it.
>
> But you sure as hell can feel what's doing it.
Maybe you ought to bolt a transducer to the floor joists,
and feed in some LF audio...
>
>
>
> > See http://www.turneraudio.com.au/htmlwebpgs02/300monobloc.htm
> > to see a sample.
>
> Nice glass bill when it time to replace 'em all.
Cheaper than nos.
And if 300 watts isn't really wanted, 12 x 6V6, 6L6, EL34, 6CA7 etc,
at 1/2 the price again could be used.
Various no loss taps on the OPT allow matching..
>
> But, if you started out with a full set of GE-6550A's, You can most likely figure you
> saved your great grand kids a pile of bucks, so they don't need to replace any tubes yet.
I wouldn't mind a quad of GE 6550A for use in a stereo 5050 amp.
I wonder how they compare to the new EH KT90?
Reports from two friends in Sydney have been very positive.
>
>
> Life extention is not measured by just one test case.
>
> Parallel that current tube, with that of the GE, and now see which lives the longest.
Maybe both would survive me.....
> So, no matter which way you want to spin the 6550 spin for those from off shore, the GE's
> are the shit.
I did buy 16 jan GE 6550, green lettering, in 1996, and I dunno if they were 'A' or not.
They have lasted reasonably well, but nothing spectacular, going
by the changes to gettering colour, and the increasing amount of grid current
even at idle.
This means the grids run maybe 1/2 a volt more positive than the
negative bias supply. Not on all the tubes, just some.
They were all very well matched 2,000 hrs ago, when new,
but not now, although all remain very usable.
Hours and hours of running wear out tubes.
If a muso's amp does three gigs of 4 hrs each a week, that's 600 hrs per
year, and perhaps you get 6 years, or 3,600 hrs but the chances of
some "incident" which causes an amp to fail, or fall off a stage or truck
is more likely yo shorten the tube life.
Random failure means some go a long time, and others don't.
> > My amps make about 200 watts of class A, and its all very relaxed
> > and the idea is to have limitless headroom for a hifi situation,
> > where effortless and distortion free sound is sought.
>
> Yeah, and class A don't beat the shit out of the screens like AB ultra linear does.
Class A stresses the tube quite highly. doing nothing, the tubes work hard.
and fairly warm, and if a galoot connects a shorted speaker
without noticing it, poof go the tubes, since thay are already quite hot.
So I for one don't try to run 6550 or KT88 like one friend of mine does,
sitting right on an average of 42 watts, +/- 10%, with some of the tubes
with slight dull red hot spots on the anodes.
I like using the opt CFB windings for local FB in the output stage rather
than use plain UL, which is very nice sounding for hi-fi, I know.
The screens can be fed from a 300 volt supply,
shunt regged, with a series R from the anode supply at say 500v or more.
Then if the screen currents are excessive, then the series R just allows
to screen voltage to sag with the excessive screen current, tending to
cut off the tube current.
>
>
> There is another example where you don't go sticking the wanna be 6550's straight, in
> where the GE's go.
>
> Why, because they ain't the SAME!!!!!
Don't worry, I will remember your advice.
>
>
>
> > In one of my 8585 hifi amps, I used 8 x jan GE6550, nos, green lettering.
> > They were about twice the price I pay now for EH6550.
> > I don't know wherther there was anything really special about them.
> > After 7 years of on -off use in a hifi situation, they all became prone to
> > grid current even at idle, and some of the grids going a volt or two positive.
> > Then I reduced the bias resistors to 100k, and they held their bias better.
>
> Well then, to exactly who's family of 6550 curves was that amp designed.
>
> The GE's, or the wanna be 6550's.
GE's. The loading on the tubes is very mild,
Only 4.4k a-a for quad of 6550, with only 480v plate supply,
and 300v screen supply.
On a good day, only 3 watts is asked of the amp.
The so called EH6550 "wanna bees" sure sounded OK when the owner recently
replaced all his tubes.
He was quite delighted.
>
>
> I KNOW, they ain't the same, so which way did the designing go here.
I started with GE, knowing that the operating conditions
were very mild.
6L6 used in the same amp deliver nearly the same power.
My use of 6550 is overkill for what I want, its like
fitting two Harley engines into a drag bike, rather than having one which is turbo
charged.
Or having two men saw the log instead of just one.
>
>
>
> > The client had me replace all the tubes with EH 6550,
> > and he said there was a big improvement in the soundstage,
> > which seemed to have depth, not only width, as before with GE,
> > then he said the dynamics and detail were improved.
>
> Like the Tungsol is to the GE, so are other tubes with the same numbers on the glass.
>
> The tube's curves are different, their windows of operation is different, their loading
> windows to the OT's are different, and the OT loading designs are different manufacturer
> to manufacturer.
>
> So, just where does this all line up for the GE. For the EH.
The EH performed almost identically yo the GEs they replaced.
There was about 5% more power.
>
>
> Get the picture.
>
> With respect to your client:
>
> What is the program material we talking about here.
>
> How long is HIS audio retention good for.
>
> Just what was the length of time between comparisons.
>
> Define his meaning of the words DEPTH and WIDTH.
> If that was made with respect to the Sonic Field, that is the biggest crock of shit I've
> ever heard!!!!!
I have no answers to your many questions.
I place my customer's wishes and opinions way ahead of my own.
My customers are king.
If they say they hear things one way or another, I'd be silly
to ignore them.
>
> Gee, I didn't know that just by changing output tubes, you could IMPACT the hardly heard
> anymore 3D sonic field, that truely escapes the clue less engineer/producers of today's
> generation
Some stereo systems provide imaging better than others, agreed?
And some are just different.
Some swear than Quad 57 ESL give the only really true imaging,
and having heard them, I could say yes, they do image well,
but only when seated in one critical position.
Many other folks don't like them at all, or Martin Logans,
and one friend says Accustats are the best by far.
Then there are the dome and cone brigade who
say the overload character of cones is far better, and they enjoy real bass
from large woofers in big boxes that go down to 20 Hz.
I ahve not owned any ESL speakers, so I don't really know if I am missing out on something.
But after recently hearing some mint Quad 57 ESL, I think not.
The amps used with such systems do have quite some effect on the sound heard,
and we run into preferences and various choices of combinations, and nearly every
person I meet who thinks past a cheapo 3 in 1 stereo for $200
has some opinions which he thinks is correct for him.
Who am I to disagree?
I just connect up the tube gear, run some music, and keep my mouth shut.
I normally get a very enchoraging response, and
if they want, I lend an amp to them for a week,
and the amp does the trick better than the existing at their house, and
after some serious listening, and comparisons, and the folks I sell to
are able to pick out the gear's differences.
>
> So, this better be a stereo system, and the program material better have that tudio
> engineered 3d sonic image, that is very rare in the history of recorded music, for me to
> take any of these claims seriously.
>
> Then likewise, Define his meaning of the words DYNAMICS and DETAIL.
>
> Hmmmmmmmm.......................!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
The 8585 in which I replaced the GE 6550 with EH 6550 was tested at first
with some Ashkenazy on piano, and I was gobsmacked.
( Sorry, I don't have the definition of gobsmacking, but....)
Anyway, sometimes you just know that the amp issa really doin it right,
when grand piano turned up loud sounds GRAND.
I have stood beside one played loudly, and they are powerful sounding
instruments, and very hard to accurately reproduce.
Worry not about other's definitions; be pleased that thay have opinions,
and that they be positive about what you create!
>
>
> <thinking>
>
> Screw it.
>
> What the hell am I supposed to do with this meaningless babble!!!!!!!!!!
>
> What,.. did we get a freq increase or band width increase here!!!
>
> What's the deal.
>
> You tell me!!!
>
> I ain't got no crystal ball.
>
> Where's the RTA, power, and impedance curves of both conditions!!!!!
>
> > Hifi amps are never subject to severe signal overloads and gross clipping
> > with rock musician amps.
>
> OK,.... I guess I just got it!!!!!
>
> Forget what I said one click above.
>
> Your client is all full of crap, and imagined it.
>
> There is NO WAY, a change of output tube can impact the sonic field of STEREO system in
> either a well mixed 3D, or the standard BS 2D most ALL of us hear from our everyday
> recordings.
Some output tubes do the whole business of making reproduced sound seem
seem real better than another set, or perhaps just as well, but with a slightly
different flavour.
Some wines are better than another, or just different, or both,
and who is the best artist, the best performer, the best bass player?
Its all in the ears of the listener.
>
>
> Long gone are the days when engineer/producers even had 3D mixing in mind when setting up
> the mics in the studio!!!!!!!
>
> So, to me, his words are meaningless!!!!!!!!
Well quite a few of my friends like old recordings done with two crossed mics sitting out in
front.
The don't like all the recordings they have purchased, and in fact think some are garbage,
and in collections of thousands of vinyls and CDs, they tell me there are only
a few real gems when it comes to recording quality.
They do at least have systems decent enough to tell them
how good, or bad, a recording is.
I don't have the time or funds to be an ardent collector of music;
I know guys who have spent 20 grand on recordings.
>
> As meaningless as the tall tails told by those who've had sex with aliens, and the baby
> produced has super hearing for things not of the real world.
Well, experience with testing speakers with cutomers present
reveals that some can hear a tweeter going up to 17 kHz .
Not many can detect sound over that, but perhaps some feel it.
Not all folks have the same number of brain cells devoted to
decoding what the ears hear, and some have no trouble understanding the garbled
screaming of the lyrics by a pop star at a loud gig, or the words of an opera sung in english.
I need subtitles for both!
BIG differences exist in ppls hearing abilities.
>
>
> > But they are left running for hours on end, day after day,
> > with a substantial bias current to allow lots of class A.
> > I guess the tubes wear out for different reasons in the
> > music amp versus the hi-fi amp.
>
> Correct!!!!!
>
> Class A is a waste of electricity, to reproduce silence!!!!!!!!!!!
Well any large tube amp even when run in class AB "wastes" lots of power.
But we cannot hear wasted power.
Some folks prefer class A power, and when only a few watts is needed,
then the waste during listening compared to a couple of lightbulbs or running a PC
to type to other folks about the subject is not very great.
Our whole lives are spent wasting things.
But I refuse to be a hermit, eating grass, and living in a cave...
>
>
> But then, look of all the tube gear of the past that was left on 24/7 in all the labs
> across this land where tolerance and calibration had to be held.
>
> Look at all the communications transmitters that required the same.
>
> There are a lot of 24/7 tube examples besides this one.
>
> So, it's the Class A, that kills ya on this one.
I don't know anyone who leaves their power amps on 24/7.
Some leave the preamps on.
Some have swimming pools, air cons, six kids, 4 cars,
and have 25 lights on inside the house at night, and they
change wives every 7 years, and if everyone lived like that,
we'd need 25 planet Earths to sustain the damage.
> So, as an enviornmentally frendly person, I use AB only for my audio needs.
>
> But, don't you dare call me a Tree Hugger!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I also use AB PP amps, but I sometimes prefer the SE amps,
and 25 watts of SE power is plenty for me.
Nothing wrong with trying to save the trees and nature from the ravages of
mankind, propelled by the needs of womenkind.
Take a good look out there.
In 1,000 years, it will be very very different.
>
> > One of the sweetest music amps I heard was 6V6 PP,
> > about 80% UL taps, nearly triode, in class A.
> > Another 6V6 in triode drove the output stage via a transformer.
>
> Look, I've had my share of Hifi gear experience through my life time. I also prefer to
> follow the laws of mother nature with respect to the natural world around me.
>
> Audiophile books are no substitute for the physics book on the subject, when it comes to
> understanding the world around you..
I use engineering theory all the time, there are no guesses at any aspect
of my productions. All is carefully reckoned, in the light of
experience.
I also listen to what my non tech clients and friends tell me.
>
>
> > This amp was one of the few which seemed to have sweetness
> > and a sort of natural reverb,
>
> Here we go again!!!!!!!!!!!!!!!!!!!
>
> Who's on first, what's on second, I don't know, third base!!!!!!!!!!!!!!!!!!!!!!!
>
> Natural room reverb, is NOT the product of ANYTHING, that has anything to do with the
> amplifier itself!!!!!!!!
>
> Natural room reverb is governed by other things!!!!!!!!!!!!!!!!!
Well it was just there.
I am quite calm about what I have no answer for.
Some things cannot be unravelled.
I do my best, but I sure don't know *every* reason for the world's
audio intricasies.
>
>
> > but without a reverb unit used.
> > The owner-builder was a physics lecturer, whose interest off campus was guitar,
> > and rocket engines.
>
> And maybe a collection of tin foil hats in the closet too.
>
> > Another client uses Sovtek 6550 in triode in a Marshall head for use
> > in his "dark metal" band,
>
> OK, now I know about that stuff.
>
> > and the sound is basically like a continual stream
> > of jumbo jets crashing on the pavement in front of you.
>
> There you go again.
Just my "old foggie" opinion.
To me it is noise, not music.
To they who enjoy it, it is whatever it is.....
>
>
> Just when I thought we were going to connect, you get weird on me again.
>
> I wouldn't have a clue what the hell the sound of crashing jumbo jets crashing in front of
> me would sound like.
dheafvfeakljvf;klvjl;sklswktlgjklwbjwdflkbjvlkbjsb!!!!!!!!!, all x 10,000 times louder .
There.
>
>
> Let alone coming from a Marshall in triode with sovtek wanna be 6550's.
>
> Pisssssssssssssssssssssssssssssst!!!!!!!!!!!!!!!!!!!!
>
> Ummmmmmmmmmmmmmm......................!!!!!!!!!!!!!!!!!!!!
>
> Ya wanna hear what I can do with a 400-PS with three full Marshall stacks on it with my
> Strat, fuzz face, vox wah, octave down box, etc.... ALL up on TEN, in full Jimi glory
> doing my version of the Star Spangled Banner!!!
>
> You think I would come close to what your friend has going on with the Jumbo Jets
> thing!!!!!!!!
Well, it most deafinatelly sound more patriotic!
>
>
> > Not my cuppa tea, but some folks think its very cool!
> > The tubes are either off, or 40 dB over clipping.
> > After 4 years, I think he's on his second pair......
> > The first pair expired after using too low a load impedance
> > when swithed to the 16 ohm setting.
> > So when I hear about tubes failing, I wonder first
> > about the human element.
>
> No, you have to wonder about the quality of the materials that are actually used in the
> tube. The purity of the vacuum of the tube. Then, the degree of vacuum when tipped off.
> These are just for starters!!!!!
>
>
> > Unlike Fender, I fit individual cathode current sensors
> > to each output tube so that if any one tube out of so many
> > misbehaves, and goes red with too much cathode current,
> > the amp is turned off.
>
> Good idea!!!!!!!!!!!!!!!
In a hifi amp, I have an SCR which trips a relay, turning off the amp
or at least turning off the B+, by switching off the HT winding on the PT.
Usually with an AB hi-fi amp, if the direct cathode current is more than twice the idle
current which may occur with clipping into say a 3 ohm load, then the amp
is interupted by the over load.
RC filters are used to damp the tripping.
Brief bursts of overload are allowed, but if such signal bursts, or for any reason the
DC at the catode increases by 100% for *more than 4 seconds*,
then off goes the amp, and all is saved.
Now this could be a bother for a muso amp where
the cathode current regularly goes higher. Perhaps some mush slower acting circuit
would be OK, still fast enough to catch a changing DC level due to a bias failure,
or tube saturation event.
I don't build musician's amps, and most get by without any active protection,
not even heat sensors mounted an inch away from the glass tubes.
With some transistors, its easy to rig up some protect circuit on small board.
>
>
> > That mightn't suit a muso, who might prefer to blow a few tubes rather than stop
> > to change to a spare amp between songs, if the fuse hasn't blown.
> >
> > Patrick Turner
>
> Oh, I see this was cross posted.
>
> That explains things a tad more.
I don't spend time posting at alt.guitar.amps,
but I don't mind this cross post, since
it is about tubes, and I work on quite a few muso amps
as well as hifi types all day long.
Regards,
Patrick Turner.
lbrt...@aol.com
> My standard for a yardstick IS the 400-PS. Because, the yardstick for the GE-6550A, was
> the 400-PS.
>
> That is how the history went.
Hmmm...sounds reasonable. Proven results is everything. I've only
had one 400-PS on the bench.
> So, re-writing history to favor the imports, is what is going on here!!!!!!
Still seems a little odd; there is other gear that runs 6550A's fairly
hot that hasn't displayed this behavior so strikingly. FWIW one which
comes to mind is a few modulators, which run them just like a 6146B.
The original 6550A is a 6146B (not plain or A) with no plate cap, and
therefore somewhat lower max plate voltage. Most tube modulator
service is comparable to hard guitar service, electrically speaking.
The 6146B was simply repackaged to be safer in consumer gear running
lower plate voltages & no RF service.
Don't wish to over-beg the question, but we'd have to admit that
running them past their design max dis (plate or screen or both), even
if some versions get away with it somewhat, is a no-no.
One might speculate whether the imports may be less internally robust
(shock/vibration criteria etc.), possibly leading to shorter effective
life in the punishing environment of a 400-PS.(?) IOW, mechanically
cheaper in ways that only show up in butt-kicking amps?
This would also seem consistent with the low-end waveform going to pot
while the rest stays reasonably happy; perhaps (SWAG) the element
spacing (and therefore capacitance & other things) could be moving or
vibrating excessively.
You'd think there would be a few mfg'r tube engineers looking in on
what goes down here, to comment or at least take interest.
Most of the older GE Beam pwr tubes seem mechanically tough. The
6L6GC's likewise seem to take remarkable punishment, especially
inverted, while I've had "black plate" RCA's and many others old &
new, not hold up as well, and some of the former with noisy elements
right out of the box.
I feel that if modern mfgr's, located anywhere, cannot make a
particular audio tube better & cheaper & more reliable than mfgr's did
40 years ago, something is hosed up, no matter what face is put on it.
lbrt...@aol.com
> > Patrick Turner wrote below: "Most pentode/tetrode guitar amps are mostly
> > class B amps, with a small % of their power in class A."
> >
> > I have never seen such a statement in any EE book?
>
> And you probably won't ever.
> But one has to describe the distinctions between class A and class AB somehow.
You are accidentally introducing some confusion, Patrick, by
re-defining operating class away from engineering criteria and toward
audiophile aesthetic criteria. In engineering terms, there is no such
thing as you describe, though many of us here do know what you mean by
it.
You also refer to "bias current", another well-intended confusion in
terms. Surely you mean the idle plate & screen currents of your class
A amps, which have their max dissipation at idle ("where they are
biased")? Tubes operating in A or AB1 draw no bias (grid) current at
all, until/unless they start to sh*t the bed.
The only valid definition of your A, is that the tubes are biased so
that both exhibit signal flow for 360 degress with no cutoff during
any part of their operation. Any & every amp meeting this criterion,
tube or solid state, is A. Anything else beyond this, while perhaps
of sonically descriptive interest to audiophiles, is irrelevant to its
class, and sows confusion in the guitar amp world.
Perhaps the eventual grid current problems you are seeing/refer to are
caused by eventual cathode stripping?
We agree about the appeal & tastefulness of clean playing (mentioned
elsewhere in your comments). Many (not all) players arrive at such a
point after a lot of experience & maturing of technique. But this
does little to assist those trying to kick butt with a 400-PS, which
some styles require.
I think it is becoming fairly obvious that people are cooking 6550's
by exceeding design plate and/or screen dissipation ratings under full
power, combined with a fair amount of mechnical punishment. A pair of
6550's is in fact good for 100w into a correct load & fed properly,
and sometimes a bit more. Certainly 135w is beyond the pale. But the
6550 is essentially a 6146B, and all these tubes are notorious for
being subject to damage from excessive screen voltages, just as you
correctly imply elsewhere. We proved all of this by experience in the
'50's & '60's, and it hasn't changed any, no matter who makes the
tube, as you also imply.
I have to wonder why someone needing a 400w reliable bass amp in 2004
is still fooling with tubes at all, but that's another can of worms.
Maybe they should build one with 813's. :-) 813's have black plates,
too<hahahah>. How's 600+w from 2 bottles sound? I suppose with 2.5kv
on the plates, they wouldn't dub with it so much...
lbrt...@aol.com
> I would guess any tube whose structural elements are rigid enough to
> maintain spacing and does not readily "short" when subject to
> shock/vibration. This can be easily determined by energizing the amp with a
> 100 Watt clear light bulb in series with the line, and with all the tubes
> installed, tapping on the tubes with a rubber handled screwdriver - while
> light would indicate structurally unstable tube elements - meaning it is
> likely the amp/tubes will short during service. Otherwise, I doubt you would
> be able to discern any quality difference. The SVT is also tough to
> balance - from what I recall, and can be very touchy.
Most people have switchable bulbs on their bench autotransformer
panel. But the sorts of element vibrations or excursions thought to
be at play (emphasis "thought") are a good deal less than a short
capable of this observation. Most experienced people tap for shorts
on a tester,too. But such shorts would be major noises and failures
in an onstage 400-PS (translation: it would quickly sh*t the bed).
Humorously, you may or may not wish to reconsider calling yourself a
PE in public discussion. It is like ship captains who call themselves
"Captain" in the company office when they are promoted to managers-
they are usually useless. :-) Besides, people can get a PE to
approve things or otherwise make them liable for what they do or say
as one. Guess why I don't<g>.
James Angelo Ruggieri, P.E.
> panel. But the sorts of element vibrations or excursions thought to
> be at play (emphasis "thought") are a good deal less than a short
> capable of this observation. Most experienced people tap for shorts
> on a tester,too. But such shorts would be major noises and failures
> in an onstage 400-PS (translation: it would quickly sh*t the bed).
I always used a bulb to not only weed out the troublesome tubes - but also
to help locate other shorts.
The bulb method is a great and reliable method - so I'm uncertain what you
are trying to say.
> Humorously, you may or may not wish to reconsider calling yourself a
> PE in public discussion. It is like ship captains who call themselves
> "Captain" in the company office when they are promoted to managers-
> they are usually useless. :-) Besides, people can get a PE to
> approve things or otherwise make them liable for what they do or say
> as one. Guess why I don't<g>.
Since you know so much about liability, I guess you also selected to forego
the JD suffix as well :)
--
JAMES RUGGIERI
<lbrt...@aol.com> wrote in message
news:205ef942.04022...@posting.google.com...
Rich Koerner
lbrt...@aol.com wrote:
>
> Rich Koerner <ri...@timeelect.com> wrote in message news:<40394415...@timeelect.com>...
>
> > My standard for a yardstick IS the 400-PS. Because, the yardstick for the GE-6550A, was
> > the 400-PS.
> >
> > That is how the history went.
>
> Hmmm...sounds reasonable. Proven results is everything. I've only
> had one 400-PS on the bench.
>
> > So, re-writing history to favor the imports, is what is going on here!!!!!!
>
> Still seems a little odd; there is other gear that runs 6550A's fairly
> hot that hasn't displayed this behavior so strikingly. FWIW one which
> comes to mind is a few modulators, which run them just like a 6146B.
> The original 6550A is a 6146B (not plain or A) with no plate cap, and
> therefore somewhat lower max plate voltage.
Back in the '60s, when someone said 6550, it was commonly associated to mean Tungsol's
6550 in my part of the electronics woods. There is a reason why GE placed and A suffix on
their 6550's. The reason, it was so re-engineered, that there was little in common with
the Tungsol's original characteristics.
The GE-6550's maximum ratings were so greatly improved, having the "A" designation makes a
lot sense.
> Most tube modulator
> service is comparable to hard guitar service, electrically speaking.
LOL, once a friend of mine used a Gibson guitar amp to modulate a 2 meter ham rig.
> The 6146B was simply repackaged to be safer in consumer gear running
> lower plate voltages & no RF service.
In very *general* terms, you are ok in saying that.
> Don't wish to over-beg the question, but we'd have to admit that
> running them past their design max dis (plate or screen or both), even
> if some versions get away with it somewhat, is a no-no.
Look, NONE of the import 6550's have what GE did to theirs. After all, THEY raised the
standards for what was commonly thought of as a 6550 here in the states. The import
companies have THEIR *Versions* of what they THINK a 6550 should be.
Published families of curves for each should represent EACH of these 6550's, and SHOW
exactly what the electrical differences ARE!!!!
There is this mistaken notion that all 6550's SHOULD *BE* the same!!!!!!
Nothing could be further from the truth!!!!!!!
If you and I can have this dialog voicing the DIFFERENCES between like numbered tubes,
THEN their family of curves should clearly represent THESE differences!!!!!!
Why Not!!!!
Are we even LOOKING at a set of the curves before we engage in their usage!!!!!
Are we even looking at the curves of these tubes, to even SEE that these tubes are even
CLOSE in specs.
Why is it, that the USER thinks that WITH all these variations of the 6550's, in reality,
ARE actually the SAME tube meeting the SAME spec. When logical thinking on the subject,
concludes, THEY ARE NOT, THE SAME at ALL!!!!!!
Why would they be the same, if we are talking about their differences!!!!!!!
Everyone of them was born from a home where their makers had no thought to see how close
THEIRS were to any of the other 6550's that already existed. For better, or worse even.
Hey, they just add an additional LETTER to the MEANINGLESS alphabet soup on the glass they
want to market to the world. This, without regard to proper standards set by those before
them, by an electronics industry that cared. In the USA anyway.
NOW, it's a bunch of wanna be tube companies MARKETING tube through the use of ALPHABET
Soup snake oil.
It's more about MARKETING, than about the proper use of Vacuum Tube Standards and
Specifications.
Are we to re-engineer the product to the bull shit 6550 tube standards of each of the
ALPHABET soup 6550's that pops of of the woodwork.
Or, are to do the re-engineering to MEET the specs of the lowest level ALPHABET SOUP 6550,
so the product WON'T HURT any of them.
THAT, is exactly the dialog, this whole thread has become ABOUT!!!!!!!!!
<thinking>
When the manufacturer of a product goes to the tube manufacturer, as did Fender with the
400-PS, and BOTH work together to ADVANCE the levels of BOTH the tube and the product
performance, and as a result, the bar is raised!!!!! THAT, doesn't now happen in this
world now!!!!!
IN the USA's past, when THE BAR WAS RAISED, the challenge had been issued to the rest of
the makers of the same tube, to meet this new raised level. History of this is seen in
the USA tube companies past meeting the challenge. Just look at the history of the 6L6
here in the states, and you will that the bar has raised many times. And USA tube
companies didn't sit on their asses and ignore the challenge. Like these BS tube
companies with their ALPHABET Soup MARKETING!!!!
Make something that will raise the bar in a 400-PS, and YOU have my attention!!!!!
Till then, it's just ANOTHER CASE, of another made up number of the side of the tube
placed on YET, another POLISHED TURD!!!!!!!!
COME ON ALREADY!!!
The GE-6550A was born in early 70 something. RIGHT!!!!!!!!!!!
So, here it is how many years later!!!!!!!!!!!!!!!!!!!
Now you tell me WHY, those clowns in the existing tube companies CAN'T produce at least
what a good GE-6550A tube did way back then.
30+ years have passed.
So, do these tube clowns KNOW anything about making a tube. Or are we going to KEEP ON,
KEEPING ON,....
the MEANINGLESS Treadmill, Of ALPHABET SOUP MARKETING!!!!!!!!!!!!!!!!!!!!!
All that yields, is the success in the marketing of POLISHED TURDS!!!!!!!!!!!!!!
And THAT, is what we have!!!!!!!!
ALL the posts ever made on usenet, where this dialog takes place, gives testament to the
fact that, an industry with integrity and standards has fallen to an industry of
meaningless ALPHABET SOUP, and the marketing of POLISHED TURDS!!!!
You SHOW ME any integrity, on the part of these so-called tube manufacturers, by their use
of this ALPHABET SOUP crap, that actually raises the bar over that of what GE, and others
had done for the past.
ARE YOU GOING TO TELL ME, THAT IMPROVING THE PAST can't be done, by ANY of these so-called
tube makers!!!!!!
Are you ALL going to PREACH to me, their recycled year after year BS excuses for not
knowing what GE knew 30+ years ago, for not making BETTER, what GE did 30+ years ago!!!!
Are they that clue less about a produce they are making!!!!!!!
What these companies are selling, and what you guys with intellectual idiocy have
embraced, I'm not buying, and I'm not having any part of.
If it don't raise the performance level of a 400-PS, it ain't a 6550A!!!!!!!!!!!!!!!
It's just another POLISHED TURD, with ALPHABET SOUP bull shit MARKETING, and IS,....
Nothing Of Substance!!!!!!!!!!!!!!!!
All other low level applications, don't count, in an exercise IN MAXIMUM ratings!!!!!!!
> One might speculate whether the imports may be less internally robust
> (shock/vibration criteria etc.), possibly leading to shorter effective
> life in the punishing environment of a 400-PS.(?) IOW, mechanically
> cheaper in ways that only show up in butt-kicking amps?
Here,.... http://timeelect.com/Book23.htm
> This would also seem consistent with the low-end waveform going to pot
> while the rest stays reasonably happy; perhaps (SWAG) the element
> spacing (and therefore capacitance & other things) could be moving or
> vibrating excessively.
Well, there is more to it.
> You'd think there would be a few mfg'r tube engineers looking in on
> what goes down here, to comment or at least take interest.
Why would any of the so-called manufacturers improve any thing. Their mojo is working!!!!
You all bought the BS hook line and sinker!!!!
Why would any USA manufacturer like GE go up against these clowns in the market place.
Simple, for the same reason they ALL bailed out of the tube industry!!!!
It became an industry of *cheap* POLISHED TURDS way back then, because consumer product
manufacturers wanted more profit, and went off shore. Just like Fender, and the rest of
them are doing today!!!!!!!
In the consumer line of tubes, RCA saw the writing on the wall first. Then one by one,
the big three closed their doors!!!!!!! Cheap off shore, killed the tube industry you'd
like to have today. But what you have is a captured marketplace where the Polished Turd
is King!!!!!!!!!!!
Hey, it is what it is!!!!! Hey, ya all wanted CHEAP over QUALITY!!!!! So, you got
it!!!!!
Look, I've talked to some of the remaining people from GE, Sylvania, and RCA, and they
laugh their asses off at how things are today. They also get tears in their eyes in
seeing an art, and a craft they were so proud of sink so low in standards. These old men
had pride in their craft, and were the men behind the achievements that is talked about,
as those great tubes of the past.
One of those guys said to me on the phone, there is simple no reason for this situation.
It is either by choice, the continuance of the cheap polished turd for the profit.
Or they REALLY don't KNOW the real science, and art of making tubes.
It's that simple!!!!!!!!!!!!!!!!!!
> Most of the older GE Beam pwr tubes seem mechanically tough. The
> 6L6GC's likewise seem to take remarkable punishment, especially
> inverted, while I've had "black plate" RCA's and many others old &
> new, not hold up as well, and some of the former with noisy elements
> right out of the box.
So based on what is left after all these years, we'd make judgment on the past.
Well, I lived though those years, and my take is a lot different. The reality of the
percentages is the opposite of what is thought to have happened. A tube failure was rare
out of the box.
I think from 1965 through 1982, I may have returned only four tubes to my distributor.
I can't buy all of what is said of the USA Tube companies. The bashing is not
justified!!!!!!
But, it's just another way to market POLISHED TURDS today!!!!!!!!!!!!!!!!
SEE, those NOS weren't very good at all back then. Our POLISHED TURDS are just as
good!!!!
BULL SHIT!!!!!!!!!!!!!!!!!
> I feel that if modern mfgr's, located anywhere, cannot make a
> particular audio tube better & cheaper & more reliable than mfgr's did
> 40 years ago, something is hosed up, no matter what face is put on it.
Yeah, you got it!!!!!
ALPHABET BULL SHIT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Rich Koerner
"James Angelo Ruggieri, P.E." wrote:
>
> What does the sound of a short-circuit sound to the * trained ear *
A shorted fuse holder.
Hmmmmmmmmmmmmmmmm...................!!!!!!!!!!!!!!!!!!!!
The lamp is only useful as a ballast, to limit line current.
It's no substitute for the human senses, and proper test gear.
> The light will brighten as current demand to the amp increases - however, a
> light brightening as a result of shock induced to the tube has nothing to do
> with sound.
Well, I guess because of the poor quality of the current imported tubes and imported
fuses, you would want to use the lamp in line to limit line current, because you can't
trust them damn imported fuses blowing out in time to protect them super audiophile audio
amplifiers. They must be real fragile too!!!!!!
God, these polished turds for tubes, must have a great history of shorts now!!!!!!
Damn!!!!!!!!!!!!!
Fuses too!!!!!
My God, I'm surrounded by Polished Turds!!!!!!
> It is also doubtful that anyone can discern any differences
> among tubes built within specification
Well, would you like to listen to the difference in the performance of a 400-PS with
GE-6550A's in it, vs a 400 with 6556-WE's after a years worth of equal mileage down a VERY
hard road.
To a player of a 400-PS, the difference is day and night!!!
You audiophile guys think you know always the last word on sonics.
LOL, yeah,... like that makes you all expert on what the musical guys use for the music
production.
Come on, jump into our world!!!!!!!!!!!!!!!!!
Besides, without us, you'd have just sound effects to listen to with your hair splitting
intensity for audio!!!!!!!
Hmmmmmmmmmmmmmmmm...........................!!!!!!!!!!!!!!!!!!!!!!!
Hey, how do you know if the harmonic content of the sound of that flute you listened to on
you audio system was, or wasn't produced by the player of the instrument originally.
Or, did a sneaky engineer like me, sneak it in on ya, as a result of my tweaks!!!!!!
How would you know the audio reproduction accuracy, both real and imagined!!!!!
Then, if I CAN do that with just a flute, imagine what fun I could have with you with the
electronic instruments.
Regards,
Rich Koerner,
Master of the sonics,
real and surreal!!!!!!
James Angelo Ruggieri, P.E.
don't you build alternatives. Perhaps you should contact one of the polished
turd manufacturers and offer your philosophy.
--
JAMES RUGGIERI
"Rich Koerner" <ri...@timeelect.com> wrote in message
news:403A7A79...@timeelect.com...
James Angelo Ruggieri, P.E.
>
> It's no substitute for the human senses, and proper test gear.
I don't know why you keep bringing up human senses or what human senses you
mean when discussing a series bulb to evaluate inrush curent - unless you
are suggesting perhaps or other body part to check the current. As for
proper tests gear - what would you use? I repaired many of these items back
when 48th Street was something other than Sam Ashe, and I always used a
light bulb - and still do today.
>
> > The light will brighten as current demand to the amp increases -
however, a
> > light brightening as a result of shock induced to the tube has nothing
to do
> > with sound.
>
> Well, I guess because of the poor quality of the current imported tubes
and imported
> fuses, you would want to use the lamp in line to limit line current,
because you can't
> trust them damn imported fuses blowing out in time to protect them super
audiophile audio
> amplifiers. They must be real fragile too!!!!!!
Seems I recall as many GE's failing the lamp/shock screwdriver test as any.
Now I see you don't like dem dar imported fuses either - I suspect this to
be a case of xenophobia.
> God, these polished turds for tubes, must have a great history of shorts
now!!!!!!
>
> Damn!!!!!!!!!!!!!
>
> Fuses too!!!!!
>
> My God, I'm surrounded by Polished Turds!!!!!!
I guess it takes one .....!
> > It is also doubtful that anyone can discern any differences
> > among tubes built within specification
>
> Well, would you like to listen to the difference in the performance of a
400-PS with
> GE-6550A's in it, vs a 400 with 6556-WE's after a years worth of equal
mileage down a VERY
> hard road.
My ears have not been circumcised as perhaps yours. Are you sure that it is
your ears that have not traveled that very hard road??
> To a player of a 400-PS, the difference is day and night!!!
Unless he or she happens to be deaf
> You audiophile guys think you know always the last word on sonics.
> LOL, yeah,... like that makes you all expert on what the musical guys use
for the music
> production.
> Come on, jump into our world!!!!!!!!!!!!!!!!!
Your world appears tainted with misinformation and apparent misguided
prejudice. I like it here - thank you.
> Besides, without us, you'd have just sound effects to listen to with your
hair splitting
> intensity for audio!!!!!!!
Without "us" -- who be "us" - I never heard your name colocating with
Lansing, Frank McIntosh, Phil Specter -- etc???
> Hmmmmmmmmmmmmmmmm...........................!!!!!!!!!!!!!!!!!!!!!!!
>
> Hey, how do you know if the harmonic content of the sound of that flute
you listened to on
> you audio system was, or wasn't produced by the player of the instrument
originally.
> Or, did a sneaky engineer like me, sneak it in on ya, as a result of my
tweaks!!!!!!
You sound like a burnt out roady - not an engineer
>
> How would you know the audio reproduction accuracy, both real and
imagined!!!!!
> Then, if I CAN do that with just a flute, imagine what fun I could have
with you with the
> electronic instruments.
Whose flute?
>
>
> Regards,
>
> Rich Koerner,
> Master of the sonics,
Self- proclaimed.
Jim Anable
> Seems you have your calling in resurrecting the GE polished un-turd -- why
> don't you build alternatives. Perhaps you should contact one of the polished
> turd manufacturers and offer your philosophy.
I'm also a GE 6550A fan. In order to reproduce it, you'd have to be able to
create the same quality plate materials, glass, etc. Then you'd need proper
tooling and quality control. This all means MONEY. Back in its day, there were
other good tubes being made (quality competition). You couldn't get away with
selling turds. When the quality of the competition decreases, the incentive to
SPEND to create a vastly superior tube also decreases. If it costs Chinese
Turdproducer twice as much and takes twice as long, with a much higher reject
rate for QC, how do you convince them to upgrade when they already sell LOTS of
tubes (turds) that cost a fraction of the time and money to make?
James Angelo Ruggieri, P.E.
Tell me - what is so deficient about these so-called turds (specifically)
and what training, education, or experience did you rely upon to come to
this conclusion?
As for the economics of the issue - seems we have quite an incentive for
enhanced tubes - given the extraordinary prices tubes and tube amps are
commanding -- no?
--
JAMES RUGGIERI
"Jim Anable" <j...@seattle-attorney.com> wrote in message
news:403A9012...@seattle-attorney.com...
James Angelo Ruggieri, P.E.
Class A;
Limited Class A Push-Pull;
Class AB; and,
Class B
Class A - means the plate current is not cut off for any portion of the
cycle
Limited Class A Push/Pull - means one valve reaches plate current cut-off
when the other valve reaches zero bias
Class AB - means overbiased and used only in Push/Pull to balance out even
harmonics
Class B - means push pull valves biased almost to the point of plate-current
cutoff
The numeral 1 following A or AB means no grid current flows during any part
of the cycles, while numeral 2 means that grid current flows for part of the
cycle.
--
JAMES RUGGIERI
"JTM50" <JT...@Shaw.ca> wrote in message news:BC5EA4CB.E250%JT...@Shaw.ca...
> Patrick Turner wrote below: "Most pentode/tetrode guitar amps are mostly
> class B amps, with a small % of their power in class A."
>
> I have never seen such a statement in any EE book?
> Are you saying that the tube in an A/B or B Class of operation can conduct
> for 360 degrees when the power is low? This can be true, however,
> What the amp does at less than full power (onset of clipping) has no
bearing
> on it's Class of operation.
>
> Lloyd
>
> in article 40395E20...@turneraudio.com.au, Patrick Turner at
> in...@turneraudio.com.au wrote on 2/22/04 5:57 PM:
>
> >
> >
> > JTM50 wrote:
> >
> >> From Patrick Turner below: "because they are substantially class A. Not
> >> totally class A, but more class A than nearly all other amps in the
output
> >> stages."
> >>
> >> This is called Class A/B1.
> >> Just cause a tube conducts for 360 degrees when it's delivering some
amount
> >> less than full power (below the onset of clipping) doesn't mean that
it's
> >> operating as Class A at that point.
> >
> > In the land of hi-fi amps, class A means that the power input
> > increases not more than 10% when clipping is reached into the rated
class A
> > load.
> > each of the tubes conducts for 360 degrees of a cycle,
> > but distortion *currents* do not have more than about 5% 2H in each
tube.
> >
> > Most pentode/tetrode guitar amps are mostly class B amps, with a small %
of
> > their
> > power
> > in class A. The tube currents in each amp cut right off, and the
> > distortion currents in each tube contain far more than 5% 2H.
> > The power input to the output stage increases dramatically, perhaps 100%
> > when full power in a low bias current AB amp is reached.
> > Class AB triode amps have much less sharp current cut off,
> > but still have more than 5% Dn in the tube currents at full power, and
as such
> > are
> > not class A.
> > A triode's anode voltage rises when that 1/2 of the OPT
> > primary swings high due to the other side swinging low by a tube being
turned
> > on.
> > The tube turning off is having rising voltage applied to its anode.
> > This rise in voltage tends to attract electrons, and the tube tries to
> > conduct more despite the negative going grid voltage.
> > In triodes, both the grid voltage and anode voltage have an effect on
the
> > electron stream, but in pentodes or beam tetrodes, the
> > effect the anode voltage has on its own supply of current is
> > much reduced due to the effect of a fixed screen voltage,
> > which screens off the electrostatic effect of the anode upon the
electron
> > stream
> > from the cathode.
> >
> > If you place a 10 ohm R in series from cathode to 0V in the output tubes
of a
> > PP
> > amp,
> > and examine the voltage at the 10 ohm R, on a CRO, all is revealed about
tube
> > currents.
> >
> > Patrick Turner.
> >
> >
> >>
> >>
> >> Lloyd
> >>
> >> in article 40393BB5...@turneraudio.com.au, Patrick Turner at
> >> in...@turneraudio.com.au wrote on 2/22/04 3:31 PM:
> >>
> >>>
> >>>
> >>> Miles O'Neal wrote:
> >>>
> >>>> Patrick Turner responded to WakyAmps, who said:
> >>>>
> >>>>>> Yes, how it is set up makes a huge difference, no a Vox AC-30 isn't
> >>>>>> really class A.
> >>>>>
> >>>>> The ones I have serviced were class A, with absolutely no feedback.
> >>>>> They had a high bias current, and each of the 4 EL84 draws about 12
watts
> >>>>> at least at idle.
> >>>>
> >>>> Now this doesn't make any sense at all.
> >>>> In Class A, full tilt isn't different
> >>>> enough from idle to make any difference.
> >>>
> >>> The input power to the 4 x EL84 is around 48 watts.
> >>> In an ideal class A amp, a max of 24 watts in class A is available.
> >>> But usually, class A max efficiency is about 40%, so
> >>> expect about 20 watts of class A from 4 x EL84,
> >>> with a few extra AB watts to make it to about 30 at onset of clipping.
> >>> Such operation is substantially class A.
> >>> In a Musical Reference hi-fi amp made in the US, Ea = 700v, Eg2 =
350v,
> >>> and power output at clip from a pair is 36 watts, but its very
definately
> >>> mainly class B, with only a couple of class A watts.
> >>> Idle power is about 5 watts per tube. During low level operation,
> >>> there is much more thd than for amps with gobs of class A power..
> >>> But nevertheless, the use of a high value RL seen by the tubes of 14k,
> >>> and 5% of CFB from a winding on the opt, and global FB, the amp
> >>> measures ok.
> >>>
> >>> Many EL84 amps are less ambitious about power,
> >>> with a quite a few good for 21 watts, such as Mesa Boogie,
> >>> some Fenders with 6V6, where the B+ is high enough, as well as
> >>> the load value, to get such power, which is well in excess of what
you'd get
> >>> if every watt was class A.
> >>> The Fender I fixed last week got 21 watts AB1 from 6V6, with 450v
supply.
> >>> BIG voltage swing, low current swing, and mainly class B operation.
> >>> The cut off behaviour of tubes is such that the crossover distortion
> >>> of such amps is not entirely awful, certainly not in a guitar amp,
> >>> where distortions are prized, and there is no such thing as really
> >>> clean operation, because it sounds so plain dull and boring.
> >>>
> >>> One is forced to allow some harmonic distortions, principally 3H,
> >>> and then boost the hell out of all the treble, add some reverb,
> >>> and maybe it sounds well.
> >>> Most guitar amps are PP mainly class B in their output stages.
> >>> Very few *pure* class A PP output stages are ever used, and
> >>> *extremely* few single ended class A output stages.
> >>> But all the input stages are nearly all SE stages using 12AX7,
> >>> so much of the warmth comes from the SE triode input stages which
> >>> are over driven a bit, and the distortion happens to be musically
appealing,
> >>> ( with a high level of 2H and 4H ), even to old smoothies, like George
> >>> Benson.
> >>> But don't ask me what Mark Knoffler uses in his amp circuit to give
him his
> >>> trademark sound.
> >>>
> >>>>
> >>>>
> >>>> So, just curious - why do you say they
> >>>> were Class A? What do you think that
> >>>> means?
> >>>
> >>> because they are substantially class A.
> >>> Not totally class A, but more class A than nearly all other amps
> >>> in the output stages.
> >>>
> >>>>
> >>>>
> >>>> ...
> >>>>> As I see it, all the 6550 from yesteryear about which ppl rave as
being
> >>>>> just so superior to
> >>>>> anything else are all actullay prone to failure from hard use,
unfortunate
> >>>>> events with the wrong speaker impedance, etc, since all the ratings
> >>>>> indicate that they are what they are, mortal tubes, and like us
mortal
> >>>>> human beings,
> >>>>> they are gonna die one day.
> >>>>
> >>>> While this is true, some of the tubes made back
> >>>> in the far exceeded their published specs, and
> >>>> hence are worth far more than the common tubes
> >>>> of today, to some people. If it'll last five
> >>>> times as long when being punished, it's worth at
> >>>> least five times the price - more if you calculate
> >>>> the lower likelihood of failure during a gig.
> >>>
> >>> But none of the tubes I have seen will take 5 times the
> >>> power dissipation of an average spec tube.
> >>> There is *no* 6550 with an anode diss rating of 200 watts,
> >>> and nealry all turn red at just over 45 watts, and then its time for
> >>> prayer, or to reach for the off switch.
> >>>
> >>> I actually like NOS US made tubes.
> >>> I have a pair of ancient 40 yr old Sylvania 6CA7,
> >>> which in UL still pump out 28 watts of class AB at
> >>> 0.125% thd with 17 dB of NFB in an ancient ex school PA
> >>> amp which I use regurlarly in my shed to test speakers etc.
> >>> It withstands the occasional red plate session, when left running into
> >>> a load which is too low. Done that a few times.
> >>> Accidently had the leads come together for awhile with a signal,
> >>> and sure, it got hot, but good as new after being turned off for
> >>> 5 minutes.
> >>> These tubes were old and tired when I bought 7 years ago sh for $3
each,
> >>> but they keep truckin. I know I ain't likely to
> >>> ever blow up a nice pair of customers speakers I happen to be testing,
> >>> simply because I'm usin a transformer coupled amp, and there is no
nasty
> >>> DC to come a leapin outa the box to fry a driver.
> >>>
> >>> I see no reason why today's tubes won't survive the "industrial use".
> >>>
> >>> I have had one sovtek KT88 get a broken heater connection on a tube
pin,
> >>> and this made the other in the PP circuit do all the work, and it went
red
> >>> for quite some time before the customer noticed, ( customers are
> >>> non techs, and notoriously slow to realize something is wrong ),
> >>> but after a resolder, the overheated tube seemed undamaged.
> >>>
> >>>>
> >>>>
> >>>>>> I'm merely suggesting
> >>>>>> that, while for Rich there's no other tube than the GE and no other
amp
> >>>>>> than the PS400, the OP is looking to retube a reissue SVT and the
OP may
> >>>>>> be quite satisfied with the Sovs (at half the price no less). And
it is
> >>>>>> the OP's needs we're trying to address here, right?
> >>>>
> >>>> Sure. I agree with you here. At the same time
> >>>> I understand where Rich is coming from. He's a
> >>>> firm believer in the value of the old tubes over
> >>>> anything built today (so far), and wants to help
> >>>> others understand that.
> >>>>
> >>>> In some case I agree with him on the state of the
> >>>> art and the value; in others I don't. Most of the
> >>>> time we're in different threads, because I mostly
> >>>> deal with 6BQ5s and 6V6s, which he dismisses as
> >>>> "radio tubes". 8^)
> >>>
> >>> The littlies have a very nice sound though, and its why dudes use
them.
> >>> For a small venue for a jazz scene, maybe its all that's needed.
> >>>
> >>>>
> >>>>
> >>>>>
> >>>>> I assure you that other folks make big tube amps. As new old stocks
of
> >>>>> favourite old tubes dry up, all we are gonna have is sovtek, EH,
Svetlana
> >>>>> etc.
> >>>>> But asking more than 75 watts per pair of bottles is asking for
trouble.
> >>>>
> >>>> With the new tubes this may be so - I don't know.
> >>>> But I have known lots of folks getting 100W or more
> >>>> per pair (think SVT!) with no problem.
> >>>
> >>> Back in the 1960's, quite a few amps using EL34 with
> >>> 800 volt B+ supplies were used, mainly for PA, because
> >>> 100 watts was available, and low THD wasn't a priority.
> >>> I probably sat thru many a sermon ( boring ) at the church
> >>> where I was taken each sunday as a kid with such amps.
> >>> Where are all those amps? all gone to the Yonder!
> >>> And these were all mainly used for just a bit of pious speach,
> >>> not kickass bass with serious overdrive.
> >>> Tube and socket replacements due to arcing were common,
> >>> so one reason they all were replaced was the spectacular
> >>> failures, costs of maintenance, and anyone selling the then very
> >>> new, and even rather expensive solid state amps had little trouble.
> >>> I don't believe they sounded all that much worse in the PA field.
> >>> Most of those have all expired and been thrown out.
> >>> Nothing is forever.
> >>>
> >>>> ...
> >>>>>> Remember, Rich claims that the GE and Sov "aren't even close"
sonically
> >>>>>> or electrically. Maybe so in his tweaked 400PS and to his ears and
> >>>>>> playing style; there may not be as strong a case in the OP's RI-SVT
and
> >>>>>> to the OP's ears and style.
> >>>>>
> >>>>> How anyone can tell much difference between the sound of tubes when
the
> >>>>> thd is at around 25%, and IMD at around 50% is beyond me.
> >>>>
> >>>> Just curios - are you a musician?
> >>>
> >>> Not now; I was in a band many years ago,
> >>> and played acoustic 12 string. I did some time in coffee lounges
> >>> with folk music; I can stil play, but I have little time.
> >>> I often have to fix guitar amps, and I hear the musician's problems
> >>> and the sound, during testing....
> >>>
> >>>> Do you care about
> >>>> tone?
> >>>
> >>> Yes, and mainly at low levels, because at gross overload levels,
> >>> the waveform is mainly a square wave, and the difference in tube
brands
> >>> does not make an enormous difference to the sound
> >>> of such energy being supplied to a speaker.
> >>>
> >>>> Do you consider your ears good?
> >>>
> >>> Good enough.
> >>>
> >>>> Because the
> >>>> sonic differences in tubes are ell documented. My
> >>>> wife and kids, none of whom play guitar (Josiah keeps
> >>>> saying he wants to, but never practices much) can hear
> >>>> these differences, and they aren't tube freaks by any
> >>>> stretch of the imagination!
> >>>
> >>> I hear differences, sure, but mainly at low levels.
> >>> The "dark metal" guy who likes his 6550 in triode runs them at
> >>> gross overload all night. I don't believe the sound would change
> >>> if he changed from Sovtek to GE.
> >>> To me it would still sound like a continuous aeroplane crash
> >>> happening right in front of me.
> >>>
> >>>>
> >>>>
> >>>> [Story of 0 ohm tube PA into < 1 ohm bins snipped]
> >>>>
> >>>>> In this case, its better to err on the load value by choosing a
value too
> >>>>> high, rather than too low!
> >>>>
> >>>> Why not try your friend's PA head into, say, 64
> >>>> ohms at full blast and let us know how that goes?
> >>>
> >>> If you have a 400 watt amp capable of 400 watts into 64 ohms,
> >>> then using 64 ohms would give only a fraction of the power,
> >>> and the sound level, because the voltage swing from the tubes is
> >>> nearly maximum even with 8 ohms, at 56 vrms, and
> >>> with 64 ohms, only 20 more swing is available, ie 67 volts,
> >>> so one gets only 70 watts. But the class A % would be quite high.
> >>> Pentode/tetrode operation is almost universally used for output stages
> >>> in the music industry in tube amps.
> >>> Distortion in such amps with a high RL is not necessarily
> >>> all that much lower than some lower value RL which is the optimal for
> >>> low thd. But high value RLs mean the output stage has much higher
gain.
> >>> If there is a feedback loop, then there is effectively much more
applied FB
> >>> with a high value RL.
> >>> The gain of a 6550 in class A with a 2 kohm plate load is about 19.
> >>> But with 16k its about 80+, or five times the gain, which is + 14 dB.
> >>> If there was 12 dB of FB applied with 2k, then there is about
> >>> 5 times the feedback applied when the load is changed to eight times
the
> >>> load
> >>> value.
> >>> Thus with 16k, there is an effective 26 dB of FB applied.
> >>> One has to be careful about stability if using a high value load, lest
the
> >>> amp
> >>> begin to oscillate at some LF or HF.
> >>> In practice, since most amps operate mainly in class B,
> >>> the open loop gain is about 1/2 what I have described, so the max
amount of
> >>> FB with a 64 ohm load would be 20 dB at high power.
> >>> But at low power, the gain is higher, since it is class A.
> >>> This explains why some poorly stabilised amps oscillate just a little
> >>> and no more, because they do so only in the operating region where the
tube
> >>> gain
> >>> is high.
> >>>
> >>> Speaker impedances rise to high values at HF, because of their
> >>> inductive character.
> >>>
> >>> So, I would never recommend that anyone use a 64 ohm load with
> >>> a pentode/tetrode amp which was designed for 8 ohms.
> >>> 16 ohms would be OK though, but 4 ohms could be deadly.
> >>> To ensure stability, even with no load at all, when the output tube
> >>> gain is perhaps 150+ then the feedback loop has to be carefully
> >>> considered, and some way of damping, ie, loading the output stage
> >>> at F above 20 kHz should be employed,
> >>> say by having an RC network with HV rated C and large wattage R
> >>> strapped across each 1/2 primary.
> >>> Some ancient amps using V1505 power triodes with 2 kV B+,
> >>> good for 1,100 watts class AB2 used adjustable spark
> >>> gaps to allow arcs to occur if the anode to anode signal voltage
exceeded a
> >>> certain
> >>> level. Little FB was used. That was the primitive approach.
> >>> But with pentodes or tetrodes, unlike triodes, the gain changes with
load,
> >>> and often some FB is used. Well concieved RC gain limiting networks
are
> >>> good practice.
> >>>
> >>> The idea of using multiple parallel KT88 or 6550
> >>> isn't new for high power.
> >>> There was a design described in full in a 1957 edition of Wireless
> >>> World, which easily tested at 400 watts with 10 x KT88.
> >>> All the parts were mounted on a piece of 3/4" plywood,
> >>> about 24" x 9", breadboard style. Class A % of the power was
> >>> substantial.
> >>> Probable use was for a stadium, theatre PA.
> >>> Poor struggling musos could never afford such gear, and all the
speakers
> >>> that went with the amp, and the van to carry it all.
> >>> There were 10 ohm resistors to each cathode of the KT88, with a meter
which
> >>> could be switched
> >>> to each 10 ohms to check the bias currents.
> >>> The tube idle power dissipation was kept low, and to allow for
> >>> uneven bias drift; such amps often have only one fixed bias voltage,
> >>> and one has to allow for one or more tube's idle current to
> >>> mysteriously escalate during its life.
> >>> Nevertheless, the tests of the 1957 amp showed it could sustain
> >>> the use of lower load values briefly, and that it was capable of
> >>> well over 500 watts.
> >>>
> >>> I believe the prudent designers then would never have considered the
use of
> >>> only
> >>>
> >>> 6 x 6550 to do the job.
> >>>
> >>> It'd be like flogging good men to death.
> >>>
> >>> Patrick Turner.
Jim Anable
> Well then -- looks like you are stuck with turds - doesn't it?
...or stuck with buying NOS.
> Tell me - what is so deficient about these so-called turds (specifically)
I'll leave the specifics to the "experts."
> and what training, education, or experience did you rely upon to come to
> this conclusion?
I have a basic electronics education that would not impress you. My dad was a
design engineer for Bell Labs, and electronics has been a hobby of mine for as
long as I can remember. I have built, modified and repaired tube amps. I have
used the 6550 for years in guitar amp applications -- applications that could
be considered "abuse" by hi-fi standards, which may be why I can detect the
difference in quality and life and you can't. I have spoken with others who
share my opinions, some of whom might be better able to explain the
"specifics."
I have an ear. I can hear the difference in how different tubes distort.
Distortion characteristics are important to guitar players. Hi-fi uses just
want clean, and they don't make the same sorts of demands on the tubes.
> As for the economics of the issue - seems we have quite an incentive for
> enhanced tubes - given the extraordinary prices tubes and tube amps are
> commanding -- no?
WE have an incentive to buy, but is the increased cost and difficulty worth it
to manufacturers that have no problem selling what they make now??? Initial
setup costs would be nothing to sneeze at.
James Angelo Ruggieri, P.E.
So you are telling me that you have no basis to conclude these other tubes
are so bad. What experts?
I consider myself an expert and it is my opinion that these other tubes are
fine. Isn't this issue a point of contention across the industry?
> I have
> used the 6550 for years in guitar amp applications -- applications that
could
> be considered "abuse" by hi-fi standards, which may be why I can detect
the
> difference in quality and life and you can't. I have spoken with others
who
> share my opinions, some of whom might be better able to explain the
> "specifics."
But I too was tempered in tube use as applied to cadence amplifiers:
Marshalls, Sun, Fender, Ampeg and so on. Yes, it is an abusive environment.
I wasn't speaking from a HiFi perspective - and I'm uncertain how you can
imply that my perspective to be HiFi based - however, I also believe that
you also cannot tell me what the difference is - aside from physical
vibration, etc issues.
> I have an ear. I can hear the difference in how different tubes distort.
> Distortion characteristics are important to guitar players. Hi-fi uses
just
> want clean, and they don't make the same sorts of demands on the tubes.
So you are telling me that distortion is desirable and important to you -
well - isn't distortion (a non-linear characteristic) a feature normally
inherent with poor tubes or poor circuits? What kind off distortion do you
speak of?
> WE have an incentive to buy, but is the increased cost and difficulty
worth it
> to manufacturers that have no problem selling what they make now???
Initial
> setup costs would be nothing to sneeze at.
And what are those setup costs? Do you know? Didn't Adam Smith say a
contestable market will invite new players - and is there not incentive for
new players to provide "non-turd" tubes? I'll tell you why there are no more
GE 6550's - its because the current manufacturers can provide a similar
product at competitive prices. They have considerably lower variable costs
than we do here in the US, and can thus offer the same tubes at a cheaper
price. As Smith also noted - price is entirely subjective, and the GE folks
knew that they would have incurred excess marketing costs in order to
mislead folks into believing that that their tubes were so much better than
the next guy's - as a means of justifying the much larger expenses. By the
way - do you know who owns GE?
--
JAMES RUGGIERI
"Jim Anable" <j...@seattle-attorney.com> wrote in message
news:403AA6D8...@seattle-attorney.com...
Miles O'Neal
>> Not quite. In a SE Class A amp, you typically get just under 50%, but
>> 45% is very easy to get.
>
> 45% is very optimistic, and represents the practical limit for class A
> efficiency.
> Most tetrode/pentode amps are 35%.
Mayeb big tubes are winpy; I mostly
play with 6BQ5s and 6V6s. I have
*never* had a problem getting more
than 40% out of a Class A amp.
>> And Push-pull Class A gets you just a little better than double what
>> you'd get with an equiv- alent SE design design of one tube, so you run
>> right about 50%.
>
> Very seldom.
> The amp doing 50% plate efficiency is usually operating with considerable
> class AB. the max efficiency of class B with tubes is around 66% only.
RCA disagres with you; it's not just me.
>> > ...with a few extra AB watts to make it to about 30 at onset of
>> > clipping. Such operation is substantially class A.
>>
>> This is where you are wrong. An amp is biased for one *and only one*
>> class of operation under its normal operating conditions.
>
> No, most amps with enough bias current will operate as pure class A amps
> with an appropriate minumum load to alow this to occur. Below this load,
> they are class AB, and above that min load, the power is all class A
NO. BY DEFINITION (yes, I am shouting
in hopes it will get your attention)
am amp is biased for a given operating
class under a certain set of conditions.
If you bias it as Class A for a certain
set of conditions (which certainly includes
the load), then within those conditions,
it is Class A. If any of the conditions
change, then you have to refigure things
for that set of conditions. And if it
comes up Class AB, then it *is* Class AB.
Not "Class A except..."
...
>> Now a Class AB amp will operate similarly to a Class A amp until the
>> signal starts reaching cutoff, but that doesn't mean the amp is Class A
>> until that point.
>
> I think your'e the one who has it wrong. One could have a class AB amp,
> each tube is operating in class A at low voltage/current swings.
> One can prove this easily. Set up a PP amp with 6L6 and Ea = 400v, and
> bias at 30 mA.
> use about a 5k a-a load.
> measure the current into the CT on the OPT. there is a region of operation
> where the current input stays constant, hence the power input is constant,
> and the amp *must* be working in class A. As soon as one tube begins to
> cut off while the other carries on, its class AB, and the power input
> starts to rise, indicating class AB.
It *does not matter* that at lower signal
levels both tubes conduct 360 degrees.
What matters is that within the operational
parameters of the circuit, at some point
each tube conducts less than 360 degrees,
then the amp is not biased class A.
Class of operation is not what the amp is
doing at any given moment, which is how
you are treating it. This is a common
misconception, and we've beaten it to
death in the past.
>
>> If a PP amp is biased so
>> that you ever reach cutoff before clipping, it's not Class A.
>
> But the cut off isn't linear in many tubes, and in amps which are
regarded
So what?
And for the record, lots of amps "regarded"
as Class A - are not Class A.
> as class A, there is still a slight increase in power input near clipping,
> because the current cut off in one tube is less than the current increase
> in the other.
Again, so what? The Class of operation is
not defined by total current consumption.
It's defined by what goes on within the
individual tubes, considering the system
as a whole.
> If the wave forms of the cathode currents are examined its
> plain to see that in a class A amp, each output tube has quite a lot of 2H
> distortion current, but not actual complete current cut off.
I'm not sure why this is relevant...
...
>> > Most guitar amps are PP mainly class B in their output stages.
>>
>> Wrong! Most of them are Class AB, not Class B.
>
> I think you misunderstand.
> Most guitar amps display full cut off of the tube *current* for most of
> the cycle at clipping with a sine wave.
The operating classes have to be defined
as cutoff before clipping occurs. Otherwise
they make no sense.
> If the amp is set up for class AB, the AB power max is about 21 watts of
> which 5 could be class A, and the remaining 16 is B, because after 5
> watts, the tubes start to cut off during the cycle. Connect a CRO to a
> cathode resistor, and you will see what happens.
There you go again. Basic electronics theory.
An amp is biased for 1, and only 1, class of
operation under its operating parameters. It
may *act* the same as a Class A amp up until
a certain point, but it either *is* or *is not*
Class A. If it exhibits the characteristics
of Class AB at any point, then it *is* Class
AB. That's how things are *defined*.
>> >... Very few
>> > *pure* class A PP output stages are ever used, and *extremely* few
>> > single ended class A output stages.
>>
>> The former is obviosuly correct, but
>> as to the latter ... there are more and more of these every day.
>
> Not much use of SE musicians amps.
Nope. The Fender Champ is still a
hugely popular amp. SE Gibson Skylarks
and Kalamazoos are still used a lot.
Check out the AX84 site. Note the
UniValve and BiValve. As I said,
SE amps are (re)gaining popularity
for a variety of reasons.
> The SE amp is a gutless wonder to many musos.
Irrelevant to this discussion.
...
>> And who said they would take that? I haven't seen anyone talking about
>> a 600W Class A SVT!
>
> Well if some of the hype about some of the sturdier 6550 brands are to
> believed, you'd think there is some magical quality, some special ability
> for the tube to exceed the ratings, but there is no magic in the ratings.
> Perhaps the cathode emisions under stress do vary over time somewhat
> earlier with russian tubes.
All I was asking was why you were arguing that
5x bit as if someone had said they would take
that.
> I have not noticed falling emissions with russian tubes, but then we
> havn't had time to evaluate this. Maybe in 30 years, some grey haired old
> bugger will hark back to his youth in 2004, and try to tell folks that
> 2004 tubes are so much better than 2034 tubes. There will be only 3
> samples left in the world of mint GE 6550 in 2034, and arguments will rage
> that perhaps they are chinese fakes....
8^)
...
>> That's not the point. You were talking about how bad it was to run an 8
>> ohm amp into 1 ohm or less, and claimed lower impedances were worse than
>> high. So I just went up the same amount you went down (8->4->2->1 vs
>> 8->16->32->64). I can guarantee that if you try that load, your tube
>> amp will fry, fry, fry. The closer you get to an open load, the worse
>> off a tube amp is.
>
> Any tube amp should be able to be used without a load up to when the
> voltage swing reaches the peak value of the supply voltage. To make sure
> the swing is limited to stop arcing. diodes from anodes to 0V can be
> added, as seen in the schematic at
>
> http://www.turneraudio.com.au/htmlwebpgs02/schem100ulabmono.htm
They're running those tubes extremely gently
compared to any guitar amp!
> There are three diodes in series to limit the negative swing of the anode
> voltages...
You just destroyed the sound of the tube guitar amp!
I *hate* the sound of diodes in plate circuits. And
I am not alone! The distortion turns to crap.
> The only reason preventing full output signal voltages with no load in
> tube amps
>
> is appalling design methods, ie, bean counters, ie, the humans failing to
> take enough responsibility for their constructions.
Nonsense. There are plenty of fried *good*
amps around from running with no load.
...
> The shorting jack is there to prevent the amp from ever seeing an open
> circuit, or no load, when it may indeed misbehave by oscillation and die
> from its poor design.
> Its very unlikely anyone will use the amp with no speaker connected.
> Nobody likes playing music at a gig in silence.
Speakers get unplugged all the time.
People switch speakers with amps plugged
in, pull cords for various reasons, trip,
knock things over, etc. Speakers blow.
It happens all the time, and flyback
effect kills lots of amps.
> All my amps can be used with or without a load, no worries. accidental
> signals taken up to clipping with no load does *zero* damage.
Good for you. Put diodes in all your plate
circuits, or just run them all at very
low power?
> With 12 tubes in my amps, I get away with separate RC cathode bias for
> each tube, in my case with 15 watt x 500 ohms with 1,000 uF per tube
> cathode.
> All the worry about biasing 12 tubes properly does not exist, since auto
> bias sets itself very reliably. The tubes get it easy in my amps, and i
> hope they last, and last, and last......
Well, there's my answer. Yeah, if you baby
it, it'll be fine. I'd hate to see what you'd
try to do building a drag racer. "No, really!
We'll put five engines in it, and never rev it
past 2000RPM. It'll last forever!" 8^P
Steve Eaton
"Patrick Turner" <in...@turneraudio.com.au> wrote in message
news:4039AB8D...@turneraudio.com.au...
Miles O'Neal
> But one has to describe the distinctions between class A and class AB
> somehow.
...
> Perhaps if you read my other posts where I try to define what is class A,
> B, and AB, et all, you may get the picture.
And that's the problem. You are trying
to *redefine* these terms. That's the
wrong answer.
You need to find a way to communicate
what you are trying to say without
violating what's already been done.
Miles O'Neal
> Are we even LOOKING at a set of the curves before we engage in their
> usage!!!!!
>
> Are we even looking at the curves of these tubes, to even SEE that these
> tubes are even CLOSE in specs.
Can we even *get* a set of curves???????????
Miles O'Neal
> What does the sound of a short-circuit sound to the * trained ear *
>
> The light will brighten as current demand to the amp increases - however,
> a light brightening as a result of shock induced to the tube has nothing
> to do with sound. It is also doubtful that anyone can discern any
> differences among tubes built within specification...
In guitar amps, it's easy. Even
untrained, non-guitarists can
hear the difference. Even drummers.
Even us trombonists. Even in a
blind test. Piece of cake.
Chocolate cake.
Yum!
Jim Anable
> > I'll leave the specifics to the "experts."
>
> So you are telling me that you have no basis to conclude these other tubes
> are so bad.
Did I say that? Please read on...
> What experts?
I don't speak for others, they will chime in if they want to. Among them are
musicians, owners of amp companies, experienced amp techs...
> I consider myself an expert and it is my opinion that these other tubes are
> fine.
This thread was posted to alt.guitar.amps. Are you also a musician? How many
different tubes have YOU experimented with in a Marshall 2204? What style of
guitar do you play? How many different guitar amps do you own? What are your
tube choices and why?
If you can't answer those questions, you're "expertise" means squat to me.
Don't assume that I'm some yahoo just because you don't know me or because you
have a different perspective on tubes. Hi-fi people with have one perspective.
Engineers may have another. Musicians, yet another, based on EXPERIENCE and
personal tastes on TONE.
I don't care what the data sheets say, I don't care what the curves look like.
I sometimes can't keep the grid and screen straight in my mind. What I care
about what they SOUND like in my gear, and how long they will perform.
The current offerings of many types of tubes are NOT "fine" with me.
> Isn't this issue a point of contention across the industry?
> > I have
> > used the 6550 for years in guitar amp applications -- applications that
> could
> > be considered "abuse" by hi-fi standards, which may be why I can detect
> the
> > difference in quality and life and you can't. I have spoken with others
> who
> > share my opinions, some of whom might be better able to explain the
> > "specifics."
>
> But I too was tempered in tube use as applied to cadence amplifiers:
> Marshalls, Sun, Fender, Ampeg and so on. Yes, it is an abusive environment.
> I wasn't speaking from a HiFi perspective - and I'm uncertain how you can
> imply that my perspective to be HiFi based - however, I also believe that
> you also cannot tell me what the difference is - aside from physical
> vibration, etc issues.
>
> > I have an ear. I can hear the difference in how different tubes distort.
> > Distortion characteristics are important to guitar players. Hi-fi uses
> just
> > want clean, and they don't make the same sorts of demands on the tubes.
>
> So you are telling me that distortion is desirable and important to you -
> well - isn't distortion (a non-linear characteristic) a feature normally
> inherent with poor tubes or poor circuits?
I thought you knew Marshalls, Sun, Fender, Ampeg...
I'm not about to give you the history of distortion in guitar amps, but what YOU
may only consider to be "inherent with poor tubes or poor circuits" is desirable
to MANY guitarists. In a sentence, it may have started with limitations of
early guitar amps, but now it is an art form.
> What kind off distortion do you
> speak of?
I was speaking of power tube distortion. However, I also have opinions on
preamp tubes. I currently have a 1958 production 17 mm plate Mullard ECC83 in
the gain position of my 2204. I can tell you that it produces a better sounding
midrange distortion in my Marshall and most of my other equipment. I've tried
many, I've had others swap tubes so I judge them blind. I prefer Mullards with
a slight preference for the long plates.
With respect to power tube distortion, my Marshall has a relatively low
impedance on the plates. Drive the power tubes hard, they distort. Different
tubes sound different when they distort. There IS a sonic difference between
brands. GE 6550A gives high output with solid low frequency response in a
2204. When they distort, they have a "metal" (harsher) sounding distortion, as
opposed to the "bluesier" (rounder, with earlier break up) sounding EL34's.
That's how they act in my amps, and that's what I care about. They also last
longer than current production tubes.
But you're the EXPERT, and you know Marshalls, so I shouldn't have to tell you
that.
> > WE have an incentive to buy, but is the increased cost and difficulty
> worth it
> > to manufacturers that have no problem selling what they make now???
> Initial
> > setup costs would be nothing to sneeze at.
>
> And what are those setup costs? Do you know? Didn't Adam Smith say a
> contestable market will invite new players - and is there not incentive for
> new players to provide "non-turd" tubes? I'll tell you why there are no more
> GE 6550's - its because the current manufacturers can provide a similar
> product at competitive prices.
Is that why NOS GE's cost so much? NOS Tung Sols? Telefunken? Mullard? Bugle
Boy? Or do you believe that it is just non "experts" that don't know any
better, and we'd all be better off with Sovteks or Chinese?
> They have considerably lower variable costs
> than we do here in the US, and can thus offer the same tubes
Do the majority of "experts" consider the current offerings to be "the same
tubes" as GE 6550A?
> at a cheaper
> price. As Smith also noted - price is entirely subjective, and the GE folks
> knew that they would have incurred excess marketing costs in order to
> mislead folks into believing that that their tubes were so much better than
> the next guy's - as a means of justifying the much larger expenses. By the
> way - do you know who owns GE?
That'd be the shareholders.
WakyAmps
>
> Back in the '60s, when someone said 6550, it was commonly
> associated to mean Tungsol's 6550 in my part of the
> electronics woods.
Speaking of which, this ought to lighten the mood a touch :)
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3079509304&category=3284
I particularly enjoyed the definition of "matched set"
Steve Eaton
"James Angelo Ruggieri, P.E." <JRugg...@Cox.Net> wrote in message
> > I'll leave the specifics to the "experts."
>
distort.
> > Distortion characteristics are important to guitar players. Hi-fi uses
> just
> > want clean, and they don't make the same sorts of demands on the tubes.
>
> So you are telling me that distortion is desirable and important to you -
Tell me that you are joking ?
> well - isn't distortion (a non-linear characteristic) a feature normally
> inherent with poor tubes or poor circuits?
Wouldn't you characterize, lets say, a Marshall amp an example
of poor circuits? By audio REPRODUCTION enthusiast standards,
I would say so. But the audiophile standards have little currency
as regards the needs and desires of musicians using the distortion to
PRODUCE
music. A different endeavor entirely from listening to music.
No, I wouldn't say that distortion is only to be found using poor tubes.
Any tube will distort if you desire it to. I would call a tube poor if the
characteristic sound of the distortion it produces is not musical to my
ears.
And I CAN hear both objective and subjective differences of the distortion
components of different tube types and brands. Some I like better than
others.
Most of my guitar amps use 6L6 type power tubes so I am most familiar
with those. In this case, just for example, every set of Sylvania's that I
have had sound similar to each other and different from let's say Sovteks.
And in every case they sound better. But that is not to say that all the
current tubes
are junk. I think that the cheap Shuguang 6L6 sounds very close to
those old Sylvanias
If you are a HiFi enthusiast, I suspect that to you, the idea that the
massive distortion
of relatively unstable circuits running tubes above their design limits,
is a desirable effect may seem odd. But millions of music fans would
disagree
as the distorted guitar amp has been one of the more widely recognized
sounds
used in music for the last 60 years.
I can understand why an audiophile might not like that sound, but I don't
understand
how an audiophile, who would certainly hear the subtle differences in the
sounds of tube types and brands when the tube is running clean, could doubt
that there are even more exagerateded differences that can be heard when a
tube
is clipping.
>What kind off distortion do you
> speak of?
Harmonic distortion for the most part I would suspect.
.
Patrick Turner
lbrt...@aol.com wrote:
> Patrick Turner <in...@turneraudio.com.au> wrote in message news:<4039691F...@turneraudio.com.au>...
>
> > > Patrick Turner wrote below: "Most pentode/tetrode guitar amps are mostly
> > > class B amps, with a small % of their power in class A."
> > >
> > > I have never seen such a statement in any EE book?
> >
> > And you probably won't ever.
> > But one has to describe the distinctions between class A and class AB somehow.
>
> You are accidentally introducing some confusion, Patrick, by
> re-defining operating class away from engineering criteria and toward
> audiophile aesthetic criteria. In engineering terms, there is no such
> thing as you describe, though many of us here do know what you mean by
> it.
Its quite difficult to describe pp amplifier operation to people who
don't do the research to find out from text books, and never bother
to examin of the wave forms in the amp.
>
>
> You also refer to "bias current", another well-intended confusion in
> terms. Surely you mean the idle plate & screen currents of your class
> A amps, which have their max dissipation at idle ("where they are
> biased")? Tubes operating in A or AB1 draw no bias (grid) current at
> all, until/unless they start to sh*t the bed.
By bias currents, I do mean the idle currents in the electrodes
The class A amps have the highest bias currents, lowest Ea,
while AB tend to have higher Ea and lower Ia.
Class B amps theoretically have zero bias current,
but in fact there are no real class B amps. All class B amps
have some minimal bias currents to minimise crossover distortions,
and so are technically class AB amps.
But such amps which are biased with the minimum Ia, just enough
to keep Xover Dn low are regarded by most as substantially class B amps.
>
>
> The only valid definition of your A, is that the tubes are biased so
> that both exhibit signal flow for 360 degress with no cutoff during
> any part of their operation. Any & every amp meeting this criterion,
> tube or solid state, is A.
The cut off character as I said in other posts is not always sharp,
especially with PP triodes, but a triode class AB amp with minimal
bias current, and where substantial cut off occurs
could never be said to be a real class A amp. Its an AB amp.
The criteria is the distortion in the tube current flow, and once the
2H exceeds 5%, or what it would be if each of the PP tubes
was loaded by 1/2 RLa-a as an SE triode, then you have moved from class A to AB.
The first 20% of the total AB watts is produced by class A action.
The final 80% by one of the pair, then the other, working
substantially alone in the power production.
The load seen by one tube during the class A part of the working is
1/2 RLa-a, and during the cycle when the other tube cuts off
the RL seen by this tube becomes 1/4 RLa-a
The class AB amp tubes see a changing load value, and the load line for
one of the tubes is not a straight line across the plate curves,
but a kinked or bent one.
> Anything else beyond this, while perhaps
> of sonically descriptive interest to audiophiles, is irrelevant to its
> class, and sows confusion in the guitar amp world.
I suggest the "guitar world" ppl do some serious study about how amps work.
I have no arguments with the opinions of audiophiles or musicians about the
sonic aspects of the sound they hear.
I am not confused about how amplifiers work, and
its because I have taken the trouble to find out by
years of study, and experience building and repairing them.
>
> Perhaps the eventual grid current problems you are seeing/refer to are
> caused by eventual cathode stripping?
Some say its leakage across the mica, which becomes ever so slightly
changed / contaminated, and when I see 0.5v across a 100k bias R, I
know I have 0.005 mA of current flow.
If the grid is at -35, and screen /anode at +400,
then there is 435 v across the mica, so the resistance is
87 Meg ohms.
>
>
> We agree about the appeal & tastefulness of clean playing (mentioned
> elsewhere in your comments). Many (not all) players arrive at such a
> point after a lot of experience & maturing of technique. But this
> does little to assist those trying to kick butt with a 400-PS, which
> some styles require.
Kick butt music has its place, but I am speaking to the whole group,
and discussions would be rather boring if we stayed rigidly
to the one subject, and never strayed.
Some will say straying OT is boring. I can't please all the ppl all the time.
>
>
> I think it is becoming fairly obvious that people are cooking 6550's
> by exceeding design plate and/or screen dissipation ratings under full
> power, combined with a fair amount of mechnical punishment.
Some folks are, for sure.
I have seen "courageous" commercial designs of amps which
boast huge powers from tiny boxes, and I am one who thinks that trend
is all BS.
> A pair of
> 6550's is in fact good for 100w into a correct load & fed properly,
> and sometimes a bit more.
Well, good for PA, or a muso.
Not for hi-fi. The thd is too high. To get 100W or more from any 6550
means you cannot have a worthwhile amount of class A power.
The amount of class A power before the amp goes into AB mode
is trifling.
> Certainly 135w is beyond the pale. But the
> 6550 is essentially a 6146B, and all these tubes are notorious for
> being subject to damage from excessive screen voltages, just as you
> correctly imply elsewhere. We proved all of this by experience in the
> '50's & '60's, and it hasn't changed any, no matter who makes the
> tube, as you also imply.
Well, some tubes have had the screen construction changed
so it can take more current, and its distance from the cathode increased slightly.
The 6L6 which first appeared had a low 300v screen rating, but the 6L6GC
will run with higher ratings.
I found the EH 6550 runs quite well with screen voltage at 300 to 350v
and the plate voltage could be anything up to 800v.
The load *must* be increased as the Ea is raised, unless one runs AB2.
For low values of screen voltage and AB1, the load must be higher value
so the negative voltage swing can be right down to
the knee in the Ra curve at Eg1 = 0V.
So if you had a pair of 6550 with Ea at 800v, and Eg2 at 330v,
then the RLa-a would be 10,666 ohms,
and the peak voltage swing would be 700v,
so the a-a rms voltage is 1,000v, and po = 93.7 watts.
If the screen voltage was lifted to 440v,
then knee in the plate curve is raised somewhat,
and a load of 8k could be used, and a-a v swing is 920v,
and po = 105 watts.
In this latter case, the max AB1 plate current is 350mA peak.
But for either of these AB1 conditions, the load line for one tube
is positioned outside the plate dissipation curve of 40 watts, and
the 8k load is well outside the Pd limit of 40 watts.
Pd = 40 watts is a conservative design figure.
EL34 were used with Ea = 900v, and Eg2 = 450v, and with a 12k RLa-a.
This gives a swing of 1,080 vrms a-a, for po = 97 watts.
If 6 k is used instead of 12k as a load, POOF!,
the tubes turn red very easily!
The max current of the 6550 is about 500mA,
and to get that one can use AB2.
One could have Ea = 600v, and Eg2 at 450v, and RL = 4ka-a,
and the AB2 v swing would be about 678 vrms,
and po = 115 watts.
If Ea = 800v, and RL = 5.3 ka-a, idle current = 30 mA,
then v swing is 961 vrms a-a and po = 174 watts.
peak plate swing is 679v and max peak current is 0.512 amps
From page 589, RDH4, and equation 15, at the bottom of the page,
we get the plate input power for 2 tubes
= 800 x ( 0.637 x 0.512 + 0.5 x 0.03 ) = 273 watts.
If output power is 174 watts, the plate efficiency is 63.7%,
a realistic figure.
The plate dissipation at 174 watts of output = 273 w - 174w = 99 w,
so about 50 watts is the dissipation per tube.
At 116 watts of output, the peak plate current is 0.418 amps,
and plate input power is 225 watts, so
plate diss is 109 watts, so 54 watts per tube.
This is all based on an idle Pd of 800v x 30mA = 24 watts of idle dissipation.
Now if somebody connects
3ka-a RL to the same amp, and we had 0.7 max peak amps in the tube,
the input power is 368 watts, and output power was 239 watts,
there is 64 watts of heat in each tube, and the anodes would fry.
At 134 watts into 3k, the peak tube current is 0.466 amps,
and Pin = 316 watts, so Pd = 182w, so each tube has to cope with 91 watts of Pd.
Should someone bias the tubes up at idle so there is say 35 watts of Pd
instead of the 24 watts, it makes matters worse.
Quite clearly, it can be seen that a quad of tubes would be required for the
174 watts of power to afford some reliability, because someone, some time
will connect a load that's too low, and cause serious damage to the tubes.
I would place the reliable design limit at 75 watts per pair of 6550 or KT88.
> I have to wonder why someone needing a 400w reliable bass amp in 2004
> is still fooling with tubes at all, but that's another can of worms.
The musicians don't like the sound from transistors, and that's why tubes are used.
But at the really big gigs, the sound comes from a tube amp, then is amplified
by the main solid state system, and the Stones have used around 140,000 watts.....
A guy I know has a system he hires out for dance parties,
with about 100 drivers in two channels forming towers about 8 metres high,
and he uses 2 x 1,200 watt SS amps with smps, quite light and small.
I visited him at a local party he had in a rock climbing venue,
and I couldn't hear myself think inside, and couldn't hear what anyone said to me.
Even with ear plugs, I could only take 5 minutes.
He'd love to have tube amps, but he couldn't afford to have me run up a couple.
The cost per watt plummets when you start building 1,000 watt tube amps,
and someone dedicated could make a 1,000 watt amp a lot cheaper
than something brand new from Crown or Crest.
But such amps are mainly all class B operation.
For class AB with at least 50% of the power in class A, the costs
soon rise.......
Patrick Turner.
>
> Maybe they should build one with 813's. :-) 813's have black plates,
> too<hahahah>. How's 600+w from 2 bottles sound? I suppose with 2.5kv
> on the plates, they wouldn't dub with it so much...
813 are not bad for some real grunt.
But there are plenty of quite small triodes with about 400 watt
plate dissipation ability providing one
forces enough air from fans through their copper
anode heatsinks These also need a highish voltage,
but some quite extraordinary power is available.
These triodes are normally used for transmitters, and are in current production,
but they can be used for AF. The ceramic-copper power tetrodes would give heaps.
At large gigs, the sound of the fans is less than the sound of the fans in the audience,
and less than the "music".
Patrick Turner
> Look, NONE of the import 6550's have what GE did to theirs. After all, THEY raised the
> standards for what was commonly thought of as a 6550 here in the states. The import
> companies have THEIR *Versions* of what they THINK a 6550 should be.
>
> Published families of curves for each should represent EACH of these 6550's, and SHOW
> exactly what the electrical differences ARE!!!!
>
> There is this mistaken notion that all 6550's SHOULD *BE* the same!!!!!!
(snip some interesting info about "polished turds", et all)
I did a search on the GE6550A.
It appears that the 16 pcs I bought in 1996 are GE6550A, the good sort of tube
you are raving about.
I looked at
http://www.tubeworld.com/6550.html
and the price of GE6550A has gone far too higgh to be worth buying,
at over US $400 for a matched quad, ( which in my experience
means little, because they don't stay matched ).
I couldn't place my hands on the spec sheets for the GE6550A,
to compare it with other versions to confirm your claims
about these tubes superior ratings.
perahps you could be so kind as to post to the group the
list of maximum design ratings of the GE6550A,
and others that you regard as inferior.
Patrick Turner.
Patrick Turner
Miles O'Neal wrote:
> On Mon, 23 Feb 2004 18:28:13 +1100, Patrick Turner wrote:
>
> >> Not quite. In a SE Class A amp, you typically get just under 50%, but
> >> 45% is very easy to get.
> >
> > 45% is very optimistic, and represents the practical limit for class A
> > efficiency.
> > Most tetrode/pentode amps are 35%.
>
> Mayeb big tubes are winpy; I mostly
> play with 6BQ5s and 6V6s. I have
> *never* had a problem getting more
> than 40% out of a Class A amp.
OK, but that is at only one value of load.
At all other values of load, you just won't get the 40%.
>
>
> >> And Push-pull Class A gets you just a little better than double what
> >> you'd get with an equiv- alent SE design design of one tube, so you run
> >> right about 50%.
> >
> > Very seldom.
> > The amp doing 50% plate efficiency is usually operating with considerable
> > class AB. the max efficiency of class B with tubes is around 66% only.
>
> RCA disagres with you; it's not just me.
I suggest you take a peak at RDH4.
>
>
> >> > ...with a few extra AB watts to make it to about 30 at onset of
> >> > clipping. Such operation is substantially class A.
> >>
> >> This is where you are wrong. An amp is biased for one *and only one*
> >> class of operation under its normal operating conditions.
> >
> > No, most amps with enough bias current will operate as pure class A amps
> > with an appropriate minumum load to alow this to occur. Below this load,
> > they are class AB, and above that min load, the power is all class A
>
> NO. BY DEFINITION (yes, I am shouting
> in hopes it will get your attention)
> am amp is biased for a given operating
> class under a certain set of conditions.
> If you bias it as Class A for a certain
> set of conditions (which certainly includes
> the load), then within those conditions,
> it is Class A. If any of the conditions
> change, then you have to refigure things
> for that set of conditions. And if it
> comes up Class AB, then it *is* Class AB.
> Not "Class A except..."
I agree with you, no need to shout to get my attention.
You repeated what I said.
>
> ...
> >> Now a Class AB amp will operate similarly to a Class A amp until the
> >> signal starts reaching cutoff, but that doesn't mean the amp is Class A
> >> until that point.
> >
> > I think your'e the one who has it wrong. One could have a class AB amp,
> > each tube is operating in class A at low voltage/current swings.
> > One can prove this easily. Set up a PP amp with 6L6 and Ea = 400v, and
> > bias at 30 mA.
> > use about a 5k a-a load.
> > measure the current into the CT on the OPT. there is a region of operation
> > where the current input stays constant, hence the power input is constant,
> > and the amp *must* be working in class A. As soon as one tube begins to
> > cut off while the other carries on, its class AB, and the power input
> > starts to rise, indicating class AB.
>
> It *does not matter* that at lower signal
> levels both tubes conduct 360 degrees.
> What matters is that within the operational
> parameters of the circuit, at some point
> each tube conducts less than 360 degrees,
> then the amp is not biased class A.
There is a transition from 360 d to less than 360,
which means it goes from class A to AB....
its not a sudden transition, especially in triode PP amps.....
>
>
> Class of operation is not what the amp is
> doing at any given moment, which is how
> you are treating it. This is a common
> misconception, and we've beaten it to
> death in the past.
Oh.
Well, I don't plan to convert all the ppl all the time.
I know class A operation when I see it, and class AB operation.
>
>
> >
> >> If a PP amp is biased so
> >> that you ever reach cutoff before clipping, it's not Class A.
> >
> > But the cut off isn't linear in many tubes, and in amps which are
> regarded
>
> So what?
>
> And for the record, lots of amps "regarded"
> as Class A - are not Class A.
>
> > as class A, there is still a slight increase in power input near clipping,
> > because the current cut off in one tube is less than the current increase
> > in the other.
>
> Again, so what? The Class of operation is
> not defined by total current consumption.
> It's defined by what goes on within the
> individual tubes, considering the system
> as a whole.
I have described what I know to be class A.
Its when each tube in a PP circuit has less than 5% thd in its signal *current*.
Once 5% is exceeded, usually its then running class AB.
>
>
> > If the wave forms of the cathode currents are examined its
> > plain to see that in a class A amp, each output tube has quite a lot of 2H
> > distortion current, but not actual complete current cut off.
>
> I'm not sure why this is relevant...
Its *very relevant*.
>
>
> ...
> >> > Most guitar amps are PP mainly class B in their output stages.
> >>
> >> Wrong! Most of them are Class AB, not Class B.
> >
> > I think you misunderstand.
> > Most guitar amps display full cut off of the tube *current* for most of
> > the cycle at clipping with a sine wave.
>
> The operating classes have to be defined
> as cutoff before clipping occurs. Otherwise
> they make no sense.
Before cut off, its class A.
After cut off, and before clipping, its class AB, simple.
>
>
> > If the amp is set up for class AB, the AB power max is about 21 watts of
> > which 5 could be class A, and the remaining 16 is B, because after 5
> > watts, the tubes start to cut off during the cycle. Connect a CRO to a
> > cathode resistor, and you will see what happens.
>
> There you go again. Basic electronics theory.
> An amp is biased for 1, and only 1, class of
> operation under its operating parameters. It
> may *act* the same as a Class A amp up until
> a certain point, but it either *is* or *is not*
> Class A. If it exhibits the characteristics
> of Class AB at any point, then it *is* Class
> AB. That's how things are *defined*.
I can't win.
>
>
> >> >... Very few
> >> > *pure* class A PP output stages are ever used, and *extremely* few
> >> > single ended class A output stages.
> >>
> >> The former is obviosuly correct, but
> >> as to the latter ... there are more and more of these every day.
> >
> > Not much use of SE musicians amps.
>
> Nope. The Fender Champ is still a
> hugely popular amp. SE Gibson Skylarks
> and Kalamazoos are still used a lot.
> Check out the AX84 site. Note the
> UniValve and BiValve. As I said,
> SE amps are (re)gaining popularity
> for a variety of reasons.
I have yet to service an SE muso amp made recently.
>
>
> > The SE amp is a gutless wonder to many musos.
>
> Irrelevant to this discussion.
Nope, because musos like to have enough power,
and PP is the cheapest easiest way to power.
There is no measurable distortion due to the diodes being in the circuit.
The reverse diode currents are extremely small.
The overload character of the amp with a speaker connected shows that
the clipped wave form has a peak voltage value less than the
value of the supply voltage.
The diodes *only* conduct when the anode peak voltage swing exceeds
the value of the plate supply, ie, when an anode voltage goes *negative*, which
afaik, never occurs when a load is connected and when over driven to the point
where
the output wave is basically a square wave.
>
>
> > The only reason preventing full output signal voltages with no load in
> > tube amps
> >
> > is appalling design methods, ie, bean counters, ie, the humans failing to
> > take enough responsibility for their constructions.
>
> Nonsense. There are plenty of fried *good*
> amps around from running with no load.
The only way to fry an amp is to have too much current and voltage
across the tubes, and I have never ever seen any tubes come to grief
when accidentally used with no load, although I have seen
arcs start from the high voltages generated, which should be limited..
>
> ...
> > The shorting jack is there to prevent the amp from ever seeing an open
> > circuit, or no load, when it may indeed misbehave by oscillation and die
> > from its poor design.
> > Its very unlikely anyone will use the amp with no speaker connected.
> > Nobody likes playing music at a gig in silence.
>
> Speakers get unplugged all the time.
> People switch speakers with amps plugged
> in, pull cords for various reasons, trip,
> knock things over, etc. Speakers blow.
> It happens all the time, and flyback
> effect kills lots of amps.
I know several musos who have me service all their gear.
I ahve never had one with trouble from a shorted output,
or an open output.
Tube amps normally cope with the temporary abuse you speak of.
>
>
> > All my amps can be used with or without a load, no worries. accidental
> > signals taken up to clipping with no load does *zero* damage.
>
> Good for you. Put diodes in all your plate
> circuits, or just run them all at very
> low power?
With a load, the peak voltage anode swing is always less than the value of the
supply
voltage.
Diodes do not limit maximum power in any way.
With diodes connected, there is no measurable increase in thd!
>
> > With 12 tubes in my amps, I get away with separate RC cathode bias for
> > each tube, in my case with 15 watt x 500 ohms with 1,000 uF per tube
> > cathode.
> > All the worry about biasing 12 tubes properly does not exist, since auto
> > bias sets itself very reliably. The tubes get it easy in my amps, and i
> > hope they last, and last, and last......
>
> Well, there's my answer. Yeah, if you baby
> it, it'll be fine. I'd hate to see what you'd
> try to do building a drag racer. "No, really!
> We'll put five engines in it, and never rev it
> past 2000RPM. It'll last forever!" 8^P
I think drag racing lacks something.
The cars can't go round corners.
Its like body building, its all vanity.
Ever see a body builder win a 1 mile race?
So, horses for courses.
Patrick Turner.
Rich Koerner
Miles O'Neal wrote:
<snip to get to the important stuff>
> NO. BY DEFINITION (yes, I am shouting
> in hopes it will get your attention)
Yeah, You have to do that sometimes.
Then there is the 50 gallon drum I keep in the back yard with a 2x4 soaking in it 24/7.
That's there so when I have to smack someone's head, to get their brain cells jump
started, I don't break the 2x4.
> Class of operation is not what the amp is
> doing at any given moment, which is how
> you are treating it. This is a common
> misconception, and we've beaten it to
> death in the past.
THANK YOU MILES!!!!!!!!!!!!!!!!!!!!!!
> Again, so what? The Class of operation is
> not defined by total current consumption.
> It's defined by what goes on within the
> individual tubes, considering the system
> as a whole.
This is the proper view to have.
> > If the amp is set up for class AB, the AB power max is about 21 watts of
> > which 5 could be class A, and the remaining 16 is B, because after 5
> > watts, the tubes start to cut off during the cycle. Connect a CRO to a
> > cathode resistor, and you will see what happens.
>
> There you go again. Basic electronics theory.
> An amp is biased for 1, and only 1, class of
> operation under its operating parameters. It
> may *act* the same as a Class A amp up until
> a certain point, but it either *is* or *is not*
> Class A. If it exhibits the characteristics
> of Class AB at any point, then it *is* Class
> AB. That's how things are *defined*.
You want to borrow my 2x4!!!!!!
> >> >... Very few
> >> > *pure* class A PP output stages are ever used, and *extremely* few
> >> > single ended class A output stages.
> >>
> >> The former is obviosuly correct, but
> >> as to the latter ... there are more and more of these every day.
> >
> > Not much use of SE musicians amps.
>
> Nope. The Fender Champ is still a
> hugely popular amp. SE Gibson Skylarks
> and Kalamazoos are still used a lot.
> Check out the AX84 site. Note the
> UniValve and BiValve. As I said,
> SE amps are (re)gaining popularity
> for a variety of reasons.
LOL, as the two sonic worlds collide in their ideals of sonic reproduction.
Both worlds are not without there surreal views on reality.
However, if given a choice which of the two is more grounded, I'll be found on the stage
playing my ass off creating the REAL Deal!!!!!!!!!!!!!!!!!!
With my tube too!!!!!!!!!!!!
> >> And who said they would take that? I haven't seen anyone talking about
> >> a 600W Class A SVT!
Because, it's not practical!!!!!!!!!!!!!!!!!!
Brute power from tubes from the low end boys, has all the highs and harmonics of the
guitar, yet all the fat fat low end on the floor soft as a pillow humming your body
cells. Nothing like AB for the POWER.
Besides, who'd carry a 600W class A SVT anyway.
Not to mention the energy cost for the silence it produces, between the notes
played!!!!!!!!!
> >> That's not the point. You were talking about how bad it was to run an 8
> >> ohm amp into 1 ohm or less, and claimed lower impedances were worse than
> >> high. So I just went up the same amount you went down (8->4->2->1 vs
> >> 8->16->32->64). I can guarantee that if you try that load, your tube
> >> amp will fry, fry, fry. The closer you get to an open load, the worse
> >> off a tube amp is.
> >
> > Any tube amp should be able to be used without a load up to when the
> > voltage swing reaches the peak value of the supply voltage. To make sure
> > the swing is limited to stop arcing. diodes from anodes to 0V can be
> > added, as seen in the schematic at
Pisssssssssssssssssssssst, over here.
Can you get on another page for a second.
ANY AMP!!!!
You said ANY AMP!!!!!!!!!!!!!!!!
Horse Hockey!!!!!!!!!!!!!!!!!
USER ERROR, USER ERROR!!!!!!!!!!!!!!!!!!!!!!!
Give me a break!!!!!!
Must be a liberal!!!!!!
Let's write a law to protect amps from *users* in error.
> > http://www.turneraudio.com.au/htmlwebpgs02/schem100ulabmono.htm
>
> They're running those tubes extremely gently
> compared to any guitar amp!
If we designed EVERYTHING to survive IDIOTS, and BABY TUBES as suggested,!!!!!!!!!!!!!!!!!
The 1967 Corvette Big Block would be the wife's car to go shopping, never exceeding 15
miles per hour, because of the clamping diodes on the gas pedal for fear she will over rev
the engine missing a shift while her foot has the gas pedal on the floor.
God forbid, the engine should ever be hurt or stressed in anyway!!!!!!
<sigh>
I can't believe we are even having this dialog!!!!!!!!!!!!!!!!!!!
This is at opposite ends of the spectrum, and the 6550 is the link!!!!!!!!!!!!!!!!
This is freaking insane!!!!!!!!!!!!!!!!!!!
Miles, you got there ahead of me, so I'm letting you run with this one.
What a waste of potential horsepower!!!!!!!!!!!!!!!!
The hell, turning 6550's into sleeping wimps, and bragging about it too.
Run them bastards in AB, and MOVE some freaking air Damn It!!!!!!!!!!!!!!!!!
Oopsie, I almost slipped my grip!!!!!!!!!!!!!!
Sorry Miles, I promise to control myself, and leave quietly.
> > There are three diodes in series to limit the negative swing of the anode
> > voltages...
>
> You just destroyed the sound of the tube guitar amp!
> I *hate* the sound of diodes in plate circuits. And
> I am not alone! The distortion turns to crap.
Not to mention, there is no chance of *Angel Hair* on the sound of the guitar!!!!!!!!
Sterile tone, is guaranteed.
Damn, Miles, I'm sorry.
I promise, I'm leaving now!!!!!!
> > With 12 tubes in my amps, I get away with separate RC cathode bias for
> > each tube, in my case with 15 watt x 500 ohms with 1,000 uF per tube
> > cathode.
> > All the worry about biasing 12 tubes properly does not exist, since auto
> > bias sets itself very reliably. The tubes get it easy in my amps, and i
> > hope they last, and last, and last......
>
> Well, there's my answer. Yeah, if you baby
> it, it'll be fine. I'd hate to see what you'd
> try to do building a drag racer. "No, really!
> We'll put five engines in it, and never rev it
> past 2000RPM. It'll last forever!" 8^P
SWEET!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Rich Koerner
Miles O'Neal wrote:
> Can we even *get* a set of curves???????????
Coming up!!!!!
http://timeelect.com/images/6550ap1.gif
http://timeelect.com/images/6550ap2.gif
http://timeelect.com/images/6550ap3.gif
http://timeelect.com/images/6550ap4.gif
http://timeelect.com/images/6550ap5.gif
http://timeelect.com/images/6550ap6.gif
http://timeelect.com/images/6550ap7.gif
http://timeelect.com/images/6550ap8.gif
James Angelo Ruggieri, P.E.
tubes
> > are so bad.
>
> Did I say that? Please read on...
Yes you did by deferring to experts - implying that you did not know. On the
other hand - you could have cited accepted industry documents, references,
or publications --but you did not. Had you offered some reasonable
scientific basis for your opinions - then it was possible you could have
swayed me.
> This thread was posted to alt.guitar.amps. Are you also a musician? How
many
> different tubes have YOU experimented with in a Marshall 2204? What style
of
> guitar do you play? How many different guitar amps do you own? What are
your
> tube choices and why?
But it manifested in alt.rec.audio.tubes. Yes, I am a musician, I play the
guitar - however, not as much as I used to. I also don't own as many guitar
amps as I used to, and I'm not familiar with the Marshall 2204 - however, I
suspect it to be similar to the characteristic Marshall line of tube amps
that prevailed in the sixties - a rot gut simple and cheap push pull audio
amplifier with intentionally substantive distortion characteristics when
subject to overdrive.
When selecting tubes for these inherently imprecise devices, I use the
following criteria:
Does the tube fit into its octal socket
Will the tube perform without denigration within the given design parameters
of the amplifier
Are the tube elements loose such as to short out when the amp is subject to
expected shock and vibration
I find it humorous that so much is made of the fine characteristics among
tubes when the application is so rough - that is, the discussions seems to
be addressing the detailed characteristics of a Formula 1 racing tire as
applied to a garbage truck. Not that I am identifying these cadence
amplifiers as "garbage" and I much prefer the sound of Stratocaster through
a rot gut Marshall than through a Polytone - however, I believe that there
is much subjectivity, rhetoric, and yes - histrionics introduced into these
discussions.
> I don't care what the data sheets say, I don't care what the curves look
like.
> I sometimes can't keep the grid and screen straight in my mind. What I
care
> about what they SOUND like in my gear, and how long they will perform.
I also don't care too much what the data sheets say owing to the fact that
the QC and reproducibility of manufacturer among the subject tubes to be
more consistent than the application of being used in inherently and
intentionally imprecise instruments.
> Don't assume that I'm some yahoo just because you don't know me or because
you
> have a different perspective on tubes.
I don't know where you got this from - I simply asked you for the basis of
your opinions. But you admit that your basis to be subjective --which is OK
> > So you are telling me that distortion is desirable and important to
you -
> > well - isn't distortion (a non-linear characteristic) a feature normally
> > inherent with poor tubes or poor circuits?
>
> I thought you knew Marshalls, Sun, Fender, Ampeg...
But I do - as explained above. I also know that their desirable qualities
are owed in large measure to their imprecise performance.
> I can tell you that it produces a better sounding
> midrange distortion in my Marshall and most of my other equipment. I've
tried
> many, I've had others swap tubes so I judge them blind. I prefer Mullards
with
> a slight preference for the long plates.
Then - you will admit that perhaps your Mullard with the long plate may not
sound so good in another Marshall amp.
> Is that why NOS GE's cost so much? NOS Tung Sols? Telefunken? Mullard?
Bugle
> Boy? Or do you believe that it is just non "experts" that don't know any
> better, and we'd all be better off with Sovteks or Chinese?
I guess the answer here is the use of the NOS - indicating scarcity. As you
know the audiophile and music business is the playing ground for some of the
most intense marketing hype and appeal to subjectivity. From Monster Cable
to all sorts of nonsense. Of course, antiques typically commands high prices
because they are scarce. The scarcity, together with the subjective hype
will result in increased prices. But, and I'm sure you will agree, that to
say that my grandmother's old Singer sewing machine will perform better than
a newer machine is a bit off - no matter how many self-made tekkies weigh in
on the matter.
I'd just like to see some scientific data to support the opinions.
Regards
Jim
JAMES RUGGIERI
"Jim Anable" <j...@seattle-attorney.com> wrote in message
news:403ACC52...@seattle-attorney.com...
James Angelo Ruggieri, P.E.
distort.
> > Distortion characteristics are important to guitar players. Hi-fi uses
> just
> > want clean, and they don't make the same sorts of demands on the tubes.
>
> So you are telling me that distortion is desirable and important to you -
Tell me that you are joking ?
No -- I'm very serious. On the one hand folks embrace the distortion
characteristics of cadence amplifiers -- while on the other hand they are
addressing tube parameters and performance that serve to reduce distortion.
Seems to be a disconnect to me.
> Wouldn't you characterize, lets say, a Marshall amp an example
> of poor circuits? By audio REPRODUCTION enthusiast standards,
> I would say so. But the audiophile standards have little currency
> as regards the needs and desires of musicians using the distortion to
> PRODUCE
> music. A different endeavor entirely from listening to music.
> If you are a HiFi enthusiast, I suspect that to you, the idea that the
> massive distortion
> of relatively unstable circuits running tubes above their design limits,
> is a desirable effect may seem odd. But millions of music fans would
> disagree
> as the distorted guitar amp has been one of the more widely recognized
> sounds
> used in music for the last 60 years.
>
Although I have designed and built both HiFi and Cadence devices, I cut my
teeth on Cadence devices, and I can appreciate and discern the performance
requirements for both. I'm uncertain if the Marshall designer(s) intended
the distortion characteristics inherent in their amps - or if it was an
unintended consequence, and the design was driven by economics. I suspect
the latter - given the period of time the general design was developed. I
love the sound of a Marshall for a guitar - and much prefer that "sound"
than say piping my guitar through a Crown DC 300, for instance. However, I
would also not pipe my CD player through a Marshall, unless I wanted to
annoy my neighbors.
I simply believe that the prevailing notions being conveyed in this forum to
dismiss Chinese and Soviet Tubes as "junk" or "polished turds" to be
unfounded nonsense - perhaps rooted in either racist or protectionists bias.
In either case, an element of ignorance seems to be present. If someone is
going to call something junk - I'd like to know why - and so far, no one has
offered anything scientifically reproducible.
Regards
--
JAMES RUGGIERI
"Steve Eaton" <steve...@hotmail.com> wrote in message
news:103lnfn...@corp.supernews.com...
James Angelo Ruggieri, P.E.
at over US $400 for a matched quad, ( which in my experience
means little, because they don't stay matched ).
And further - "matched" on a production jig often does not mean "matched"
in your amp!
--
JAMES RUGGIERI
"Patrick Turner" <in...@turneraudio.com.au> wrote in message
news:403AE90C...@turneraudio.com.au...
Patrick Turner
Rich Koerner wrote:
Miles O'Neal wrote:> Can we even *get* a set of curves???????????
Coming up!!!!!
http://timeelect.com/images/6550ap1.gif
http://timeelect.com/images/6550ap2.gif
http://timeelect.com/images/6550ap3.gif
http://timeelect.com/images/6550ap4.gif
http://timeelect.com/images/6550ap5.gif
http://timeelect.com/images/6550ap6.gif
http://timeelect.com/images/6550ap7.gif
http://timeelect.com/images/6550ap8.gifRegards,
Rich Koerner,
Time Electronics.
http://www.timeelect.com
Thanks for the set of curves.
The only one which wouldn't dowload properly was no 8.
They refresh my memory, and I must say there is nothing particularly
new to learn that I can tell from the last time I saw these specs.
I also cannot see that the specs convey any greater ability when compared
to
the EH6550 that the russians make.
A word about the russian 6550.
There seem to have been 4 versions of the 6550 coming from russia.
there was the Sovtek red lettered 6550, with parallel glass bottle,
similar in shape
to the GE 6550.
Then there was the Sovtek KT88, with a small coke bottle shape,
and then the EH6550, and EHKT88, with a larger coke bottle shape,
similar to MOV KT88.
These last three appear to have exactly the same looking electrode
structure within, and all the samples I have measured at random
had the same Ra, Gm and U.
The Gm is slightly less than GE, and Ra slightly higher.
The engineer at EH said they have altered the tube a little,
and apparently the grid is slightly larger dia, which explains the
lower Gm and higher Ra.
It makes mass production easier.
But he refused to answer my questions as to why there seem to be
the same internals to tubes labelled 6550, and KT88.
Methinks it because of modern marketing, where
they sell more output tubes if they have all the types available, and
since
the KT88 is so close to 6550, then they might as well use the same
rationalised
electrode structure, because users will never figure out why this is
so, and not
care about any difference between the old KT88and 6550 which may have
been in favour of either.
That is how I see the situation with russian 6550/KT88.
I have never used or compared Svetlana 6550/KT88 myself,
but I did supply a pair of Svet 6550 in a mono Leak 60
to a guy who has used as a foldback amp without any trouble for the
last 6 years.
I could be wrong about EH, since I have never toured the factory daily
for a week or two recently.
I have serviced amps using Sovtek KT88 which are now 5 years
old, and used daily for a few hours.
These are idling at about 400v x 55 mA in Quad II very modified amps,
and running in triode.
When I measured the tubes this week during their latest service,
the maximum power level had not detectably moved downwards,
and the gettering still appears as bright as it should be after 5 yrs,
and there is little grid current at idle.
I think they are ageing just as well or better than the GE tubes I
also have
used and witnessed.
The curves you have tendered so kindly to us all do not contain info
wherin it is explained how to get 175 watts from a pair.
I figured one would have to use AB2, and an 800 v value for Ea,
and an RL about 5.3k a-a.
Just what conditions allow 560 watts from a sixpack?
If thast's the claimed max output power, then allowing for transformer
losses of
10%, the output power at the anodes at clipping would be 616 watts.
Is this the maximum possible with 40 dB of over drive, ie, max square
wave po?
But since it is possible to get 125 watts ( sine wave, at clipping )
from a pair of EL34,
I guess it would be possible to get 175 watts from 6550.
I prefer the mode of operation mentioned at
http://timeelect.com/images/6550ap3.gif
where Ea = 400v, Eg2 = 310v, and
Po = 40 watts, with only 0.7% thd into a 5 k load,
with plate current for the two tubes
starting at 170mA, and rising to 185mA at clipping.
This means each tube is idling at 34 watts plate dissipation,
and at clipping the input power is 74 watts, and since
output power is 40 watts, efficiency is 54%,
so because the efficiency is over the class A maximum of about 40%,
the test amp is a class AB amp with 5k as the load.
If the rated load was say 8k, po would be less, and perhaps 34 watts,
and the amp would then be class A nearly up to clipping, because efficiency
woukld be about 45%.
The GE 6550A when used in UL gives about 34 watts of pure class A
into 8k and 53 watts of AB into 5k, as seen in this schematic at
http://www.turneraudio.com.au/htmlwebpgs02/schema5050ulabinteg.htm
Notice that I used Ea = 515v.
A picture of the amp is at
http://www.turneraudio.com.au/htmlwebpgs02/5050Integrated.htm
This amp has Sovtek KT88, but it'd do *exactly* the same thing with
EH6550/KT88.
I seem to remeber the KT88 originally had a higher screen rating, which
meant
you could run UL with up to 600v.
Leak made a 60 watt mono amp which used 6550/KT88 which made 65 watts
into 4.5k in UL with 50% UL taps.
From what I know, the only way to relatively safely get more power from
any 6550/KT88
is to use a high Ea between 600v and 800v, and keep Eg2 down at
no more than 440v, and drive it class AB1 into a high value load as
I mentioned in other posts.
One Mr Jute in another thread about 6SL7 and milspec BS rated tubes
at r.a.t.
said he thinks 6550 and KT88 are poor tubes if you want real music,
and my answer to this
generic criticism of his is that KT88/6550 are not inherently bad,
and the sound you get depends how the tubes are used.
To me, using such tubes to get 100 watts or more from a pair
negates what I set out to do.
If I made such power from a such a parsimonius amount of glassware,
I would fail to conform to my idea of measuring well enough
to have any chance at conforming to my standard where the amp both
measures well and sounds quite glorious.
The guitarist who likes folks to feel the chest heave, and see the walls
sway
may well like to do all that with a minimum of tubes, and expensive
ones at that,
but it is a case of false economy, imho.
The distortion he puts up with, and enjoys, ranges up from a percent
at low levels to perhaps 50%.
Is there a difference in an amp sound where you have a pair driven into
overload to make 150 watts sounds any different to a quad of tubes
using a lower B+,
but making the same over driven 150 watts, and with the same
% over drive, ie, the samilar wave form?
Methinks the quad of tubes might last longer than the single pair flogged harder.
I am of a frame of mind where I would never be attracted to any venue
where
people are trying to make their guitar amps work a bit.
At 17, I was, and the power used by a 3 peice band and singer maybe
only ever totalled
300 watts, for a typical large local community hall.
They often used the same one big amp, and nothing was driven much into
clipping.
But now power is cheaper than ever before, and bands tend to
try to headbang their way through the night, and the sound levels are
20 dB over where
they were when I was 17.
The musos keep the audiologists in work.
I was strollin down town here the other night, and 4 young turks between
16 and 18
all drressed in black with chains were strivin to entertain 100 strong
crowd
with their rumblings and snortings, and dismally they showed not any
talent to be able to sing or play a tune. But they could be heard several
blocks away.
They had so much gear, so much power, so much volume, so much "attitude",
and nothing else. Its a shame that most who start like this will be
deaf
and poor by the time they realise they have to learn to
play, and learn music, and how to sing, before they would ever get
the
break that would give them a decent income.
I am far more concerned about the sound of the first 5 watts.
So, are the russian cathodes fragile? do they "go soft"
sooner than the GE us made cathodes?
Where is the evidence that russian grids and screens can't take as much
dissipation
compared to the nos us made tubes?
What is causing the alegedly inferior russian tubes to wilt under the
pressure
which the GE tubes are supposed to be able to take?
Patrick Turner.
kyser
> I'm uncertain if the Marshall designer(s) intended the distortion
characteristics inherent in their amps - or if it was an unintended
consequence, and the design was driven by economics. I suspect the latter -
given the period of time the general design was developed.
AFAIK, the intention of Jim Marshall, and Ken Bran (the designer) in early
1962 was to build a more powerful version of the original Fender Bassman
amp, given both the high price of imported US gear in the UK at the time,
and the concurrent demand by local groups (eg Clapton, Beck, Pete Townshend)
for louder amplification than the existing VOX AC30s, Selmers etc.
Mimicking Fender, they initially chose 5880s and 6L6s for the output tubes,
then KT66s (which gave more power and distinctive distortion) from January
1964 to December 1965 as the US tubes became hard to get) , and finally the
cheaper and far more available EL34s from early 1966, as the supply of KT66s
also dried up.
The amp (soon designated the JTM45) was an immediate success when demo'ed in
Marshall's London music shop, and achieved instant fame and fortune when
used (and overdriven with a Gibson Les Paul) by Clapton on the John Mayall
Bluesbreakers "Beano" album.
The rest is history .....
Patrick Turner
"James Angelo Ruggieri, P.E." wrote:
> and the price of GE6550A has gone far too higgh to be worth buying,
> at over US $400 for a matched quad, ( which in my experience
> means little, because they don't stay matched ).
>
> And further - "matched" on a production jig often does not mean "matched"
> in your amp!
>
I might add that matched does not mean matched for
Gm right across the operation range.
This means that in an AB amp, which most PP amps are,
the there is quite a bit of difference in the transfer curve
for the top half of the wave compared with the bottom half, since
each tube only does its own half of the wave.
The result is lots of 2H in PP in a PP amp.
Musos should really like this trait with unmatched tubes.
But purist hi-fi ppl might find that the thd of the PP amps they own could have
up to 12 dB less thd if only the tubes were matched for Gm, and not
just for a given bias current for the same grid bias voltage.
The use of adjustable signal drive to the output grids allows an owner to
reduce 2H distortion in PP amps to a minimum if he wishes.
Many PP amps, even class A types, where the maximum of cancelling of
2H distortion occurs, could have their thd further reduced by deliberately
trimming the drive voltages to the PP grids.
Unfortunately, a CRO and distortion analyser is needed to do this, and when
tubes are
renewed, the old setting is wrong, and the thd may be worse.
So equal drive voltages to each op grid is what most folks settle for.
But in fact, users of stereo amps may find that
one channel makes 3 times the thd of the other.
I guess that providing thd is below 0.2 % at 10 watts no matter
what the lack of matching is, then the music isn't spoiled.
Trimming is sometimes hard to do; it is in the Quad II amp.
In a pair of these I serviced this week, thd at 5 watts was able to be reduced
about 10 dB max by simply swapping the EF86 and KT66
around for lowest thd.
Amps with an LTP driver stage are easier to deal with.
Patrick Turner.
James Angelo Ruggieri, P.E.
--
JAMES RUGGIERI
"kyser" <no-...@nowhere.com> wrote in message
news:403b53f7$0$4249$afc3...@news.optusnet.com.au...
James Angelo Ruggieri, P.E.
Where is the evidence that russian grids and screens can't take as much
dissipation
compared to the nos us made tubes?
What is causing the alegedly inferior russian tubes to wilt under the
pressure
which the GE tubes are supposed to be able to take?
Doesn't seem to be any real evidence
--
JAMES RUGGIERI
"Patrick Turner" <in...@turneraudio.com.au> wrote in message news:403B4EBA...@turneraudio.com.au...
James Angelo Ruggieri, P.E.
in the cadence arena - where distortion is embraced with the utmost
affection :)
--
JAMES RUGGIERI
"Patrick Turner" <in...@turneraudio.com.au> wrote in message
news:403B5754...@turneraudio.com.au...
RonSonic
>Thank You Miles!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
>
>
>
>Miles O'Neal wrote:
>
><snip to get to the important stuff>
>
>
>> NO. BY DEFINITION (yes, I am shouting
>> in hopes it will get your attention)
>
>
>Yeah, You have to do that sometimes.
>
>Then there is the 50 gallon drum I keep in the back yard with a 2x4 soaking in it 24/7.
>
>That's there so when I have to smack someone's head, to get their brain cells jump
>started, I don't break the 2x4.
Ahh, the Patented Koerner Klue-Stick (tm).
Ron
Miles O'Neal
>> RCA disagres with you; it's not just me.
>
> I suggest you take a peak at RDH4.
I spend quite a lot of time in Radiotron,
thanks very much.
>> NO. BY DEFINITION (yes, I am shouting in hopes it will get your
>> attention)
>> am amp is biased for a given operating class under a certain set of
>> conditions. If you bias it as Class A for a certain set of conditions
>> (which certainly includes the load), then within those conditions, it is
>> Class A. If any of the conditions change, then you have to refigure
>> things for that set of conditions. And if it comes up Class AB, then it
>> *is* Class AB. Not "Class A except..."
>
> I agree with you, no need to shout to get my attention. You repeated what
> I said.
It's not at all what you said.
A given amp is one thing or the other.
It's Class A, or it's Class AB, or
whatever class you design it for.
But you have consistently said it's
Class A until this point, then it's
Class AB.
Those are *not* the same things.
I hadn't noticed the cross-posting,
or I'd have had a better idea where
you are coming from, and not gone
into some of the things the way I
did, as our worlds don't overlap
as much as some folks think.
> There is a transition from 360 d to less than 360, which means it goes
> from class A to AB.... its not a sudden transition, especially in triode
> PP amps.....
That's why I got frustrated enough to
shout. You really don't seem to be
listening.
I explicitly stated that a Class AB
amp operates with its tubes conducting
360 degrees until the signal reaches a
certain point. But it's *still* a Class
AB amp, even at those low signal levels.
You could speak of it as "operating in
a Class A manner" or something. But it's
*not* Class A up to some point. By
definition. Neither you nor I get to
change those definitions. Not unless
we achieve a much higher level of
importance in the EE world. 8^)
>> Class of operation is not what the amp is doing at any given moment,
>> which is how you are treating it. This is a common misconception, and
>> we've beaten it to death in the past.
>
> Oh.
> Well, I don't plan to convert all the ppl all the time. I know class A
> operation when I see it, and class AB operation.
But the behavior at low signal level is
not the class of operation!!!!!!!!
You seem to be defining the class of operation
by the behavior you see *at a given moment*,
when it's properly defined by the worst (or best,
depending on your viewpoint 8^) case scenario,
by what it does at the edge of its parameters.
...
>> Again, so what? The Class of operation is not defined by total current
>> consumption. It's defined by what goes on within the individual tubes,
>> considering the system as a whole.
>
> I have described what I know to be class A. Its when each tube in a PP
> circuit has less than 5% thd in its signal *current*.
>
> Once 5% is exceeded, usually its then running class AB.
This is a wonderful theory, and probably helps
you do all sorts of cool stuff. But it's not
the way class of operation is defined, so it's
horrible communication.
>> > If the wave forms of the cathode currents are examined its plain to
>> > see that in a class A amp, each output tube has quite a lot of 2H
>> > distortion current, but not actual complete current cut off.
>>
>> I'm not sure why this is relevant...
>
> Its *very relevant*.
Feel free to explain. But don't forget to
tie it into the accepted definitions, OK?
>> The operating classes have to be defined as cutoff before clipping
>> occurs. Otherwise they make no sense.
>
> Before cut off, its class A.
> After cut off, and before clipping, its class AB, simple.
You keep repeating this in various forms, but
*it's still wrong*.
If it can go into cutoff before clipping
within the design parameters of the amp,
it's Class AB, *period*. The fact that
it behaves as if it were Class A up until
that point is irrelevant.
A spy may operate as if s/he is a loyal
citizen. But s/he's still a spy. S/he's
not a loyal citizen between the times
s/he's reporting home. S/he's only a loyal
citizen if s/he *never* reports back to
the foreign government. Applying your
definitions, s/he's a loyal citizen
most of the time, because s/he isn't
actually sending reports to the foreign
power at that moment.
>> > If the amp is set up for class AB, the AB power max is about 21 watts
>> > of which 5 could be class A, and the remaining 16 is B, because after
>> > 5 watts, the tubes start to cut off during the cycle. Connect a CRO to
>> > a cathode resistor, and you will see what happens.
>>
>> There you go again. Basic electronics theory. An amp is biased for 1,
>> and only 1, class of operation under its operating parameters. It may
>> *act* the same as a Class A amp up until a certain point, but it either
>> *is* or *is not* Class A. If it exhibits the characteristics of Class
>> AB at any point, then it *is* Class AB. That's how things are
>> *defined*.
>
> I can't win.
Not if you keep trying to make up the
rules as you go, no, you can't!
Look...
I don't think the operating class definitions
are that useful in the real world. The way
you think is the way I would *like* to think.
But it's technically invalid.
So as I said, feel free to use some other
terminology. "Operates like Class A until
cutoff" or something. Otherwise you just
perpetuate the confusion.
...
>> Nope. The Fender Champ is still a
>> hugely popular amp. SE Gibson Skylarks and Kalamazoos are still used a
>> lot.
>> Check out the AX84 site. Note the
>> UniValve and BiValve. As I said,
>> SE amps are (re)gaining popularity
>> for a variety of reasons.
>
> I have yet to service an SE muso amp made recently.
That's fine. The more recent ones haven't
needed much service, by all accounts. And
they don't tend to get as much abuse as the
big amps, since they're more suited to home
and studio use, or very small venues. But
they're around, and growing.
I don't see much in the way of triode-based
stereo gear, but that doesn't change the fact
that it's there, popular, and wonderful at
what it does.
OTOH, I mostly work on smaller amps (30W and
under), and about half the amps I see are SE!
>> > The SE amp is a gutless wonder to many musos.
>>
>> Irrelevant to this discussion.
>
> Nope, because musos like to have enough power, and PP is the cheapest
> easiest way to power.
See above. Not everything is about raw
power. Your bias (sic) is showing!
...
> There is no measurable distortion due to the diodes being in the circuit.
> The reverse diode currents are extremely small. The overload character of
> the amp with a speaker connected shows that the clipped wave form has a
> peak voltage value less than the value of the supply voltage.
> The diodes *only* conduct when the anode peak voltage swing exceeds the
> value of the plate supply, ie, when an anode voltage goes *negative*,
> which afaik, never occurs when a load is connected and when over driven to
> the point where
> the output wave is basically a square wave.
I'll look into that some more. Thanks.
...
> The only way to fry an amp is to have too much current and voltage across
> the tubes, and I have never ever seen any tubes come to grief when
> accidentally used with no load, although I have seen arcs start from the
> high voltages generated, which should be limited..
Fried sockets, fried OTs, which can lead to
fried tubes. I *have* seen these, and heard
of lots more. But the amp dies whether the
tubes die or not.
...
> I know several musos who have me service all their gear. I ahve never had
> one with trouble from a shorted output, or an open output.
> Tube amps normally cope with the temporary abuse you speak of.
Most of them do, most of the time.
It's still not a good idea.
The only amps I've seen die from shorted
outputs were SS amps. But it's suboptimal
for tube amps as well. Just not as bad
as an open. I'm sure that running
a tube amp flat out into a short for a
prolonged period would eat the tubes.
But I have seen amps die almost instantly
from an open, esp. when being run hard.
>> > All my amps can be used with or without a load, no worries. accidental
>> > signals taken up to clipping with no load does *zero* damage.
>>
>> Good for you. Put diodes in all your plate circuits, or just run them
>> all at very low power?
>
> With a load, the peak voltage anode swing is always less than the value of
> the supply
> voltage.
> Diodes do not limit maximum power in any way. With diodes connected, there
> is no measurable increase in thd!
There are other forms of distortion... 8^/
Perhaps they don't matter as much in your
world, but they do have an impact in the
guitar amp world.
...
> I think drag racing lacks something.
> The cars can't go round corners.
> Its like body building, its all vanity. Ever see a body builder win a 1
> mile race?
It is what it is. [shrug]
And a guitar amp is what it is, and a
stereo hifi amp is what it is. Lugging
a 6 tube head around would be bad enough.
I can't imagine lugging a 12x6550 head
around.
I don't have my newer RCA handy. How
much heater current does that puppy pull?
Miles O'Neal
> Where is the evidence that russian grids and screens can't take as much
> dissipation compared to the nos us made tubes?
>
> What is causing the alegedly inferior russian tubes to wilt under the
> pressure which the GE tubes are supposed to be able to take?
>
> Doesn't seem to be any real evidence
Did you even read what Rich said
earlier? The GE6550A was engineered
to be much more robust than the 6550
(note lack of "A" suffix). Just as
the 6L6GC is much more robust than a
6L6, 6L6G, or 6L6GB.
I've yet to hear of anyone claiming
to replicate the 6550A. They all just
say (AFAICT) 6550. I have owned several
amps that needed 6L6GCs If you dropped
a 6L6 or 6L6GB in my Peavey Heritage
(130W from four tubes, running either
550 or 575V on the plates, I forget
which), how long do you think they
would last?
I suppose it's possible that there
are some, somewhere, that could take
it, but that's hardly the norm.
James Angelo Ruggieri, P.E.
> earlier? The GE6550A was engineered
> to be much more robust than the 6550
> (note lack of "A" suffix). Just as
> the 6L6GC is much more robust than a
> 6L6, 6L6G, or 6L6GB
Yeah - I read what everybody had to say. What does "more robust" mean and
how was this determined. Also, how does this assertion map to the Russian
tubes? Everyone I speak to, and personal experience shows the Russian tubes
to be as good if not better than the GE's. Now if you have something
specific in mind, then identify what the shortcomings are in these "foreign"
tubes.
--
JAMES RUGGIERI
"Miles O'Neal" <m...@rru.com> wrote in message
news:pan.2004.02.24....@rru.com...
Miles O'Neal
here, since the original posts haven't
showed up...
JAMES RUGGIERI
"Patrick Turner" <in...@turneraudio.com.au> wrote in message news:403B4EBA...@turneraudio.com.au...
Rich Koerner wrote:
Miles O'Neal wrote:
> Can we even *get* a set of curves???????????
Coming up!!!!!
http://timeelect.com/images/6550ap1.gif
No, Rich. I meant for the EH and other
current production tubes!
The curves you have tendered so kindly to us all do not contain info
wherin it is explained how to get 175 watts from a pair.
...
But since it is possible to get 125 watts ( sine wave, at clipping ) from a pair of EL34,
I guess it would be possible to get 175 watts from 6550.
I'm with you - this would make me a wee bit nervous.
But it makes sense.
...
One Mr Jute in another thread about 6SL7 and milspec BS rated tubes at r.a.t.
said he thinks 6550 and KT88 are poor tubes if you want real music, and my answer to this
generic criticism of his is that KT88/6550 are not inherently bad,
and the sound you get depends how the tubes are used.
Most tubes can sound good in the right
application. Some are more robust than
others.
I don't think Mr. Jute has many followers
in AGA. 8^)
...
The guitarist who likes folks to feel the chest heave, and see the walls sway
may well like to do all that with a minimum of tubes, and expensive ones at that,
but it is a case of false economy, imho.
The distortion he puts up with, and enjoys, ranges up from a percent
at low levels to perhaps 50%.
If it sounds right, and it feels
right, and the guitarist can afford
it, who is to say it's a false
economy? (Although at some point,
the guitarist had better find
someone to start producing 6550As
again. 8^)
Is there a difference in an amp sound where you have a pair driven into
overload to make 150 watts sounds any different to a quad of tubes using a lower B+,
but making the same over driven 150 watts, and with the same
% over drive, ie, the samilar wave form?
Normally, yes, because you're operating in a different
portion of the tube's range.
I can get the same power from a 6BQ5 at 250V
or 300V. At 300V, I can get incredible clean
tones, but it's harder to get pleasing musical
distortion (I know, an oxymoron in the hifi
world). At 250V, it's easy to get the distortion
tones I want, but the clean isn't as nice.
Methinks the quad of tubes might last longer than the single pair
flogged harder.
Undoubtedly. But for a gigging musician, there's
the minor problem of carrying the amp around,
nevermind having to keep spare tubes.
I am of a frame of mind where I would never be attracted to any venue where
people are trying to make their guitar amps work a bit.
That's fine, but a lot of folks are!
I am far more concerned about the sound of the first 5 watts.
Understandable. But that won't go very far with
a bass amp on stage, esp. with a drummer!
-Miles
Miles O'Neal
> "James Angelo Ruggieri, P.E." <JRugg...@Cox.Net> wrote in message
> news:mLH_b.1328$Ri6.387@lakeread04...
>
>> I'm uncertain if the Marshall designer(s) intended the distortion
> characteristics inherent in their amps - or if it was an unintended
> consequence, and the design was driven by economics. I suspect the latter
> - given the period of time the general design was developed.
>
> AFAIK, the intention of Jim Marshall, and Ken Bran (the designer) in early
> 1962 was to build a more powerful version of the original Fender Bassman
> amp...
Right.
By all accounts, Mr. Fender didn't originally
plan for distorted sounds. But they took off,
and he grudgingly accepted that. (Many of his
engineers did not, and after Leo left the company,
they drastically cleaned up the sound, annoying
many, many customers).
Jim Marshall, OTOH, wanted to duplicate the Bassman
sound, then listened to the musicians, some of whom
wanted distortion and some of whom didn't. So he
was intentionally including some.
But some of the sound *did* come from the parts
available in the price range. Design meets luck,
and a star is born.
Peter Völpel
> I have described what I know to be class A.
> Its when each tube in a PP circuit has less than 5% thd in its signal *current*.
>
> Once 5% is exceeded, usually its then running class AB.
An amplifier is class A when it is biased for class A
and always conducts therefore 360 degrees.
There is no level where it transits to class AB.
An amplifier biased for AB is still no class A, even the
tubes conduct 360 degrees up to a certain level.
Peter
Miles O'Neal
> "James Angelo Ruggieri, P.E." wrote:
>
>> and the price of GE6550A has gone far too higgh to be worth buying, at
>> over US $400 for a matched quad, ( which in my experience means little,
>> because they don't stay matched ).
>>
>> And further - "matched" on a production jig often does not mean
>> "matched" in your amp!
>>
>>
> I might add that matched does not mean matched for Gm right across the
> operation range.
Buying matched tubes from someone whose
matching techniques you don't know is a
crapshoot.
They need to be matched at the correct
operating parameters, or as close as
possible.
Matches sets on ebay? If I was going to
buy those, I'd want to get several sets
and send them off to Lord Valve or
someone for real matching. (In fact,
I once bought tubes from a friend, who
bought them on enay but didn't like
them in his amp, and sent them off to
LV. The "matching" was way off as
delivered from ebay via my friend...