4 ohm head through a 16 ohm cab?
Quick346
The other day my friend asked me the age old question (one that I keep
forgetting the answer to): Is it okay to run his 4 ohm Fender head through a 16
ohm / 300w Marshall cabinet?
I know one 'should' always match the impedance, but would there be any
problems? In this situation the speaker load would be generating more
resistance than the 4 ohm amp output, so I am assuming there would only be a
power loss, am I correct? ...or do I have this backwards?
I've searched the internet for this simple question and haven't found the exact
answer and I'd hate to see him ruin either his head or cab (or both).
We live and learn, so any help would be appreciated, thanks!
PMG
That would be bad for the amp. It would be better to have a cabinet
with LESS ohms than the amp wants with a tube amp. I stepped in the
middle of a thread like that maybe a year ago, and I had the answer
backwards (oops) and I was corrected till I was blue in the face. So
the general rule of thumb is, get the ohms speaker right, or use
speakers with less ohms, but NOT more ohms.
Pete
--
I've been shoved off better doorsteps than yours,
I can assure you --Mr. Natural
Sent via Deja.com
http://www.deja.com/
Quick346
Ahh, I will pass on the news (as well as log it in my brain). Thank you very
much!
It seems everything I've ever read on the subject explains so much about load
and resistance and impedence that they forget to simply list the rules (4 ohm
head into 16 ohm cabinet = bad) in layman's terms.
We aren't all (nor do we all inspire to be) electronics engineers! Some of us
just don't want to blow up our stuff! =)
PMG
This was one of my favorite explanations when I insisted in knowing why
it was a bad idea to use speakers with more ohms than the amp asked for.
This was by Ken Gilbert, now it's tattooed in my mind which way to go
with the ohms. Thanks Ken and everyone else who responded a while back:
>>start of file<<
Awright, pete, since LV's and duncan's reply wasn't wordy enough, here
I go now:
The crux of the problem lies in the--as LV pointed out--the inductive
nature of the output tranny. Inductive loads are pretty special
things, since they STORE energy in a magnetic field. A property of
this effect, as has been pointed out, is that the voltage can soar to
levels _above_ the supply voltage in the amplifier--sometimes WAY
above. You can't do that with any other kind of load other than
inductive.
Now the transformer doesn't have an impedance of it's own; it only
reflects an impedance from one winding to another in proportion to the
turns (or voltage--they are the same) ratio squared.
So imagine that you've got an open secondary. This impedance is for
all intents and purposes infinite. Thus, regardless of the turns
ratio, the primary impedance is infinite as well. (leakage inductance
and parasitic capacitance--two unavoidable nasties of real-world
trannies--will limit this to some finite number less than infinity, but
suffice it to say it's damned high.) This means that the primary will
act like a constant current source, attempting to keep changes in
currents through its windings to a minimum. This will be an important
point later.
Operating into such a humungous load impedance will cause the plate to
swing HUGE voltages, according to V=IR. Especially with
tetrodes/pentodes, which are much better at cranking out current, the
delta Ip will stay the same regardless of the load. Consider what
happens when the R goes sky high.
Now, if the load were NOT inductive, the maximum possible voltage
generated would be equal to the rail voltage. No problem. This is how
it is in SS amps. But with tube amps, that's not the case.
The primary danger here is in the development of these extraordinarily
high voltages, which can punch through winding insulation, arc over
tube sockets, even arc inside the tubes themselves. Once an arc has
struck you can be pretty damned sure it will happen again. And again.
This is not good. Probably the worst scenario is that the OPT primary
arcs to the core, which is grounded, and that will cause mega current
to flow. The OPT is toast, and the power supply will be too unless
something stops that current in a fucking hurry.
So that's what can happen with too high a load. Admittedly, this is an
extreme case scenario here, where you've got an OPEN secondary, and
thus a very very high primary impedance to work into.
Notice above how i pointed out that tetrodes/pentodes will have a worse
time of this than triodes. This is because of their much higher
dynamic plate impedance, which can also be described as their being an
approximation of current sources. The pentode will just keep cranking
out plate current--regardless of what potential the plate is. The
electrostatic shielding effect of the screen grid continues to "pull"
electrons from the cathode with the same force. Thus the plate current
is largely independent of the plate voltage, a mark of high plate
impedance. That current is what "builds up" (so to speak) when working
into a high load impedance and generates the excessive voltages. It's
almost as if you've got a constant current load (the unloaded OPT) on a
constant current generator (the plate of the pentode)--obviously if
these two devices are "concerned" with currents, not giving a shit
about the voltages involved, you can get some pretty crazy effects.
With a triode, the much lower plate impedance limits the extent to
which the plate voltage will swing about uncontrolled. As the plate
swings high, for example, the attraction of electrons from cathode to
plate will increase due to the higher voltage. More electrons will be
pulled to the plate, regardless of what the control grid is doing.
More negatively charged electrons means less positive voltage, so the
voltage is "automatically" decreased. This is a direct measure of
plate impedance.
In fact, running a triode into a very high impedance is done all the
time with interstage transformers, which generally are very lightly
loaded. The inherent degeneration in the plate circuit keeps the peak
voltages from becoming a problem. Actually, triodes "love" current
loads of very high impedance--the tube is operated in its most linear
fashion and is free to do what it does best--generate an output
VOLTAGE.
You can think of the dynamic plate impedance of the tube as forming a
voltage divider, with the inductive tranny between plate and B+, and
the tube itself between plate and ground. Obviously, with the low
plate impedance of a triode, the voltage cannot swing madly about. Now
consider the very high plate impedance of a pentode, and how much
higher those plate voltages can swing.
Ok, that's the situation of too HIGH a load impedance. So what about
too LOW of an impedance? Let's consider a dead shorted secondary on
the OPT.
Now the primary presents a very low load to the tube, a low impedance,
a vertical load-line. We will notice that the tables have exactly
turned.
Since the triode's plate is like a voltage source, it will attempt to
pass incredible amounts of current in a heroic attempt to make the
plate voltage swing. Operating into a dead short, it cannot do this,
so something eventually will give. The cathode will attempt to emit
way more electrons than it can, and it will have a short, hot life.
The pentode, however, is more of a current source, so it will continue
to pass the total plate current in accordance with the screen voltage
and the control grid voltage. These have not changed with the
alteration of the load, so the pentode will continue to merrily pump
its current swings into a dead shorted load.
Take a look at some plate curves, if you need to. Find some for
pentodes and for triodes. Better yet, find some for the same power
pentode connected as a triode (g2 connected to anode).
First the pentode case: look at the way the curves lie on the page.
Imagine a horizontal load line (infinite load, open secondary) drawn on
the graph. Notice how the pentode doesn't look like it would work this
way--an infinitesimal control grid voltage change would produce a
gargantuan change in plate voltage. The tube is NOT happy. Now
imagine a vertical load line (zero load, shorted secondary). The
pentode's peak current for a given control grid voltage doesn't change
much at all--the vg1=0 plate curve is nearly horizontal for most power
pentodes, cutting right across all of the various plate voltage
points. It doesn't matter what Vp is at all--no matter where you draw
that vertical line, the peak plate current is pretty much the same.
The tube is happy.
Now the triode case: imagine the horizontal load line now. Notice how
the plate voltage is almost PERFECTLY proportional with respect to
control grid voltage. No matter which tube you try, or what current
you draw that horizontal line at, it will be VERY linear. The tube is
happy. Then consider the shorted output tranny case, with a vertical
load line. Notice how the vg1=0 curve will produce a humungous plate
current since the plate curves are so much "steeper" than the pentode's
case. The tube is NOT happy.
What the hell does all this mean? Well, hopefully you aren't running
ANY tube amp into a shorted or open load... Since no pentode is a
perfect current source, and no triode is a perfect voltage source, the
actual characteristics are somewhere between the two idealized cases.
As LV pointed out, you're much better off running a pentode amp into a
lower load impedance than it expects. For those of you with triode
output tubes, or a triode switch, you're better off running into a
HIGHER load impedance. If you don't see why by now, reread this damned
essay. It's also a good idea to take a high value power resistor, say
470R, and hard wire it right from the OPT secondary's 16R tap to
ground. This will dissipate a very small amount of power under normal
conditions, but will limit the extent to which the primary impedance
will tend towards infinity in the case of a disconnected load.
For what it's worth, I've been deliberately "mismatching" load
impedances by one tap for years. In other words, either a 4R or a 16R
load on an 8R tap, and so on. This small mismatch will limit output
power and will change the clipping points of the output tubes, but will
not damage anything in a properly designed amplifier. Keep in mind
that a higher load impedance in a pentode amp will put additional
stress on the screens, so you may want to have at least 1k stoppers
installed. A lower load impedance will cause more plate current to
flow, and if you're running the tubes at the edge of acceptable
quiescent plate dissipation that may push them over the edge into the
red zone. If you've got an old vintage amp you'd hate to see get
damaged, by all means, play it safe and don't mismatch at all. But if
you're wondering about how it sounds, and the amp's got good trannies
in it, then mismatch away. Just keep it within ONE TAP please, for
safety's sake.
Ken Gilbert
>>end of file<<
Tony Hwang
Just rule of thumb. If you can't have perfect match, lower impedance
head
driving high Z cab is better(?)=safer than the other way around.
Consideration on efficiency set aside of course. So my answer is yes.
Best of all for the season.
Tony
cjt&trefoil
leading to damaging transients. There might be enough safety factor built
in, but then again ...
CompUser
"Tony Hwang" <> wrote ...
> Hi,
> Just rule of thumb. If you can't have perfect match, lower impedance
> head
> driving high Z cab is better(?)=safer than the other way around.
> Consideration on efficiency set aside of course. So my answer is yes.
> Best of all for the season.
> Tony
Tony, are you talking tube or solid state amps?
I understood that with tube amps, a lower-impedance speaker load
was safer...even a dead short was better than a higher speaker load,
which could result in a fried output transformer.
Solid state, the opposite---higher loads, up to infinity, are ok, but
low impedance or shorts are deadly.. ...?
Steve
Miles O'Neal
>
> The other day my friend asked me the age old question (one that I keep
> forgetting the answer to): Is it okay to run his 4 ohm Fender head through a 16
> ohm / 300w Marshall cabinet?
NO!
That's going the wrong way round if you
have to mismatch. He might well fry his
output tubes and tranny, and arc his sockets.
-Miles
It's like watching a horror movie, yelling
"don't go in there - he'll kill you!"
Miles O'Neal
>
> Quick346 wrote:
> >
> > The other day my friend asked me the age old question (one that I keep
> > forgetting the answer to): Is it okay to run his 4 ohm Fender head through a 16
> > ohm / 300w Marshall cabinet?
>
> NO!
>
> That's going the wrong way round if you
> have to mismatch. He might well fry his
> output tubes and tranny, and arc his sockets.
Assuming of course, that we are talking
Fender *tube* head. If it's SS, he's
probably OK.
crow
volume is seriously attenuated but the tone gets nice & hairy at the lower
volume. It works great for those live gigs where you can't crank it up or in
the home studio where bleeding into the drum overheads might be a problem.
I have never had to replace the OT, tubes or experienced any arcing. I
realise that going over a 100% mismatch is not reccomended with a Fender
amp, but this is my experience...
epp
Miles O'Neal <m...@rru.com> wrote in message
news:3A46EB18...@rru.com...
Miles O'Neal
>
> Hi,
> Just rule of thumb. If you can't have perfect match, lower impedance
> head driving high Z cab is better(?)=safer than the other way around.
> Consideration on efficiency set aside of course. So my answer is yes.
Only for solid state amps. For tubes its the other way round.
-Miles
TB1000
You got got that completely wrong. It's dangerous to tube amps to use
speakers with ratings less than the output of the amp. It's safe to use
a 16 ohm cab with a 4 ohm amp. There will be less output and a little
more distortion. DON'T USE A CAB WITH LESS OHM RATING THAN THE AMP,
YOU'LL BLOW THE OUTPUT TRANSFORMER. No problem with solid state amps
though.
Ken
Quick346
Ok, so now half of you are saying it's ok and the other half are saying it's
bad?
Here's some more stats:
Fender tube head from the mid 60's, not sure which model, haven't seen it yet,
he just got it and said it's a 4 ohm version.
His cab is just a typical Marshall 16 ohm / 300 watt Celestion jobber.
Not worried about attinuation or speaker damage, he just wants to make sure he
doesn't fry his transformer or tubes.
My opinion was that the volume would be reduced but there was no risk to
damaging anything. But then I started thinking more about it and told him to
hold off until I could find something more on the subject.
I'm not an electronics wiz and don't intend to be, I just need a reference site
so I can memorize (and maybe even print out) the rules for future reference.
Thanks again to everyone...
Ericb
it's fine as long as the cabinet is rated at a higher (NOT LOWER)
impedance than what the amp is looking for.
ERIC
In article <20001225151924...@ng-fl1.aol.com>,
Lord Valve
>You got got that completely wrong.
LV: No, he didn't, and that means you get an LV
online ass-whuppin' fer Christmas.
>It's dangerous to tube amps to use speakers with
>ratings less than the output of the amp.
LV: No, it isn't...unless the output stage runs
triodes. Most guitar amps don't.
>It's safe to use a 16 ohm cab with a 4 ohm amp.
LV: No, it isn't. You can refer to the repost of
Ken Gilbert's excellent explanation (earlier
on this thread) if you want the technical
mojo, but in a nutshell a pentode output stage
that's driving an upward mismatch is prone to
flyback, which can cause arced sockets, popped
HV capacitors, punctured insulation on wiring,
and even primary-to-core shorts in the OPT.
Don't do it.
>There will be less output and a little more distortion.
LV: This is true for any output impedance mismatch
with a transformer-coupled output stage.
>DON'T USE A CAB WITH LESS OHM RATING THAN THE AMP,
>YOU'LL BLOW THE OUTPUT TRANSFORMER.
LV: Since power is limited by the impedance mismatch,
this is unlikely.
>No problem with solid state amps though.
LV: Absolutely wrong, and this advice can cost someone
an expensive set of output transistors. As the load
impedance approaches zero, the current through the
output devices approaches infinity...or tries to.
Unless the amp has excellent current limiting
circuits, smoke will be produced long before
infinite output current is achieved. Don't do it.
Newbies, keep your eye on this dude, and don't
take his advice. You risk your gear if you do.
Lord Valve
VISIT MY WEBSITE: http://www.nebsnow.com/LordValve
I specialize in top quality HAND SELECTED NOS and
current-production vacuum tubes for guitar and
bass amps. Good prices, fast service.
NBS Electronics, 230 South Broadway, Denver, CO 80209-1510
Phone orders/tech support after 1:30 PM Denver time at 303-778-1156
VISA - MASTERCARD
"The researches of many commentators have already thrown
much darkness on this subject, and it is probable that, if they
continue, we shall soon know nothing at all about it" -Mark Twain
Lord Valve
LV
Jack A. Zucker
news:ericb-25120...@arc5a249.bf.sover.net...
> Well now it's 51% for it's fine, because it IS fine.. With your tube amp,
> it's fine as long as the cabinet is rated at a higher (NOT LOWER)
> impedance than what the amp is looking for.
>
> ERIC
if "(NOT LOWER)" than why does fender have an external speaker jack running
in parallel with the main output jack?
Jaz
--
Jack A. Zucker
E-Mail: j...@jackzucker.com
Jazz Guitar Page: http://www.jackzucker.com
Odin
Quick346 <quic...@aol.com> wrote in message
> Here's some more stats:
>
> Fender tube head from the mid 60's, not sure which model, haven't seen it
yet,
> he just got it and said it's a 4 ohm version.
>
> His cab is just a typical Marshall 16 ohm / 300 watt Celestion jobber.
Why not just rewire the cabinet for 4 ohms? If it is currently 16 ohms then
it probably has (4) 4 ohm speakers wired in series. Just rewire the
speakers with (2) speakers in series for 8 ohms, and the other (2) speakers
in series for 8 ohms, then run the two pairs of 8 ohm speaker sets parallel
for a 4 ohm final load. That way you'll have the correct impedence cabinet
and it won't cost you a cent. If you change amps you can rewire the
cabinet - or you could wire the cabinet both ways and add an extra jack on
the cabinet so it has a 4 ohm or a 16 ohm jack, but that would require a
little more work.
Tony Hwang
This is the way I remembered over the years. That's what theory tells
too. What do you think is frying the speakers? The voltage or current.
Tony
Robert M. Braught
>
> Well now it's 51% for it's fine, because it IS fine.. With your tube amp,
> it's fine as long as the cabinet is rated at a higher (NOT LOWER)
> impedance than what the amp is looking for.
>
> ERIC
No, No. Lower load than rated output impedance is *preferable* to higher
load than rated output impedance (amplifiers with tube output stages and
an output transformer, such as the Fender amp referenced as the origin
of this thread.)
*Preferable* for criteria as Lord Valve has mentioned; mismatched
impedance is still 'bad', and transformers/designs that aren't 'robust'
(I hate that 'new' word) won't take it.
The Fender in question falls into the 'usually robust enough' category.
Cheers,
Robert
QTS
http://www.Braught.com
John A. Buffaloe
an 8 ohm load. Mine has no load indication on the back, though I've seen
them that say MINIMUM 4 ohm load. Since many cabs are 8 ohms, I'm assuming
the Bassman (67 model year I believe) was intended to have as many as two 8
ohm loads running in parallel. Seems to me it would match best with an 8
ohm load. Any help here?
Robert M. Braught
At the risk of being accused of relating 'anecdotal' wisdom, I'll offer
that for the Bassman Amp of your stated vintage, numerous people around
here use them all the time at 8 ohms without any evidenced problem.
The fact is it will put out a bit more power if terminated by 4 ohms,
its actual rated impedance (two 8 ohm loads plugged in; the jacks on the
back are wired in parallel; or one 4 ohm cab.)
-Robert
PMG
A Bassman amp wants 4 ohms, I'm pretty sure all Bassman do. If you are
running it with 8 ohms, it really won't sound as good anyhow, it will be
a lot muddier than it's supposed to be. If you have two 8 ohm speakers,
wiring them parallel would give you 4 ohms, and 4 ohms is what you'd
want.
Ericb
internet dozens of times over. I've read this for years, and now this is
the 1st thread where the opposite is being portrayed. Oh well.... LV
should know more than I on this subject as he does this for a living. Me,
I"m a guitarist!
ERIC
In article <3A47C25B...@ix.netcom.com>, Lord Valve
Miles O'Neal
>
> Ok, so now half of you are saying it's ok and the other half are saying it's
> bad?
You'll never get a consensus; there are too many
people repeating something they heard when they
actually don't know what's going on.
Trust Lord Valve. Read his answer, or go to
aga.rru.com and look in the technical FAQs.
Anything that makes it into the FAQs will be written
by techs or by technically savvy people, not just
some guy who read a book or thinks he remembers what
his former bassplayer's mother's dog's favorite hash
slinger said.
(At the very least it will be edited from wisdom
by said techs and/or engineers.)
-Miles
cjt&trefoil
about induced voltages on the primary side of the output transformer in a
tube amplifier.
Lord Valve
> WELL , son of a bitch.. That'll teach me to recite theory I"ve read on the
> internet dozens of times over. I've read this for years, and now this is
> the 1st thread where the opposite is being portrayed. Oh well.... LV
> should know more than I on this subject as he does this for a living. Me,
> I"m a guitarist!
>
> ERIC
Lord Valve Speaketh:
Actually, this thread pops up every month
or so. It always winds up the same way,
too...the guys who know their shit tell
everyone that it's not a good idea to run
a tube amp at a higher load impedance
than it's looking for, and a bunch of
other dudes chime in with "Oh Yeah? I
ran my (whatever) into a 16-ohm cabinet
for years and it was rated for 8 ohms.
What about that?" Well, this is what
about it: sometimes it'll be OK. Things
are different from amp to amp; playing
style and signal type factor into the
equation, too. A player who plays loud,
with lots of treble, through an amp with
high plate voltage (old Marshall, Orange,
Music Man, older Ampegs, etc.) is much
more likely to wind up with arced sockets
(or worse) than a dude who plays jazz,
with bassy tone, through a Fender amp
with 430V on the plates. The type of
mismatch matters, too...running an 8-ohm
amp into a 16-ohm cabinet is less likely
to cause problems than running a 4-ohm amp
into a 16-ohm box. Running a downward
mismatch will eat your tubes up a bit faster,
but if your amp has a good output tranny
that's probably the only thing that will
happen. Older Fenders have an extension
speaker jack that's wired in parallel with
the main one; if you plug an extension
cab into a Twin Reverb (for instance)
the load will be lower than 4 ohms, no
matter what the box is rated at. If the
amp was going to be damaged by running a
load that was lower than the rated impedance,
it stands to reason that Fender would have
wired the jacks in series. They didn't,
though. A downward mismatch is usually
OK, or at least it's better than the upward
variety. I see a few Super Reverbs every
year that have been re-speakered by their
owners; they go to a lot of trouble to find
out how to do a series-parallel hookup for
the speakers because they "know" that the
amp should be running an 8-ohm load. All
of a sudden, the amp starts sounding like
shit and blowing fuses. A Super Reverb
wants a 2-ohm load; running it at 8 ohms
pretty well guarantees you'll be making a
substantial contribution to the Lord Valve
Home for Lord Valve. (My favorite charity.)
Of course, there will be a few "experts"
who are convinced that SS amps and tube amps
respond to improper loading in the same way.
They're wrong, no matter how loudly they may
screech.
As far as solid state amps go, it's a lot
more straightforward...if you go below the
rated impedance, you're going to smoke
something unless the amp has really good
current limiting in the output stage.
Running a higher-than-rated impedance is
just fine...you get less power output,
of course, but the amp will run cooler
and last longer. You can run a SS amp
into an open circuit 'til the cows come
home, and it won't do jack shit to it.
Run a tube amp into an open, and you'll
probably arc a socket (or worse) with the
first note you play. It's a really common
failure; I do three or four a week, year
in, year out. So Sayeth the Lord.
Lord Valve
VISIT MY WEBSITE: http://www.nebsnow.com/LordValve
I specialize in top quality HAND SELECTED NOS and
current-production vacuum tubes for guitar and
bass amps. Good prices, fast service.
NBS Electronics, 230 South Broadway, Denver, CO 80209-1510
Phone orders/tech support after 1:30 PM Denver time at 303-778-1156
VISA - MASTERCARD
"Great fleas have little fleas
Upon their backs to bite 'em
And little fleas have lesser fleas,
And so ad infinitum"
-DeMorgan, (1915)-
TB1000
I don't understand. What you're saying is completely opposite of
anything I've ever heard before. Not that I'm doubting you, I'm sure
you're right. I'm confused and sorry if I misled anyone.
Ken
AOCrowley
Lord Valve <detr...@ix.netcom.com> wrote in message
news:3A47C210...@ix.netcom.com...
> TB1000 wrote:
>
> >You got got that completely wrong.
> LV: No, he didn't, and that means you get an LV
> online ass-whuppin' fer Christmas.
>
> >It's dangerous to tube amps to use speakers with
> >ratings less than the output of the amp.
> LV: No, it isn't...unless the output stage runs
> triodes. Most guitar amps don't.
I think from TB1000's sentence below we can correctly
assume (as Lord Valve did) TB1000 meant impendance
ratings less than the output of the amp. Not to downgrade
LV's fine ass whuppin' delivery here, but the guy did say
'speakers with ratings less than the output of the amp' as in
"2 watt" am radio speaker with Fender PS400 head.
But you know, context is everything.
HEH
> >It's safe to use a 16 ohm cab with a 4 ohm amp.
> LV: No, it isn't. You can refer to the repost of
> Ken Gilbert's excellent explanation (earlier
Btw, Santa went gift wild on my ass this year.
And here I was thinking I'd get a whole coal mine.
Merry Xmas Folks.
-AOCrowley
AOCrowley
I just noticed I made up a new word: impendance.
HEH
Speaking of impendance, sometimes I get bored and start
X-filing (you know, big fish tales n the like) fer entertainment
value. Recently I stumbled on a site called http://www.earthfiles.com
that has some pretty odd pictures of mutilated cattle in Upstate NY/
Toronto area. AFAIK, we havn't had a whole lot of this kind of
thing around here, but maybe some of you folks out west are more
familiar with this kind of thing.
Anyone want to posit some theories of what's/who's doing this?
-AOCrowley
AOCrowley <j...@mindspring.com> wrote in message
news:gA026.171684$DG3.3...@news2.giganews.com...
John A. Buffaloe
Got it! Thank you!
John A. Buffaloe
head. Assuming the output tranny can handle the mismatch at 8 ohms, the
worst thing that's happening is that I'm getting less power (which is fine)
but also poorer frequency response (which ain't so cool) and maybe a little
higher distortion? Great, I thought I was done with G.A.S., now I gotta
find a 4 ohm single 12 cab!
Quick346
>aga.rru.com and look in the technical FAQs.
>Anything that makes it into the FAQs will be written
>by techs or by technically savvy people, not just
>some guy who read a book or thinks he remembers what
>his former bassplayer's mother's dog's favorite hash
>slinger said.
>
Yeah, that's what I'm going to do. I'll read the FAQ (and also trust LV) and
pass on the info. And like Odin said, maybe I'll take a peak inside the cab
and see what is going on. Seems it would be optimal to wire it into a 4 ohm
cabinet if possible....
Thanks again everyone!
Simply Steve
Lord Valve wrote:
(a whole lotta good shit, plus...)
> As far as solid state amps go, it's a lot
> more straightforward...if you go below the
> rated impedance, you're going to smoke
> something unless the amp has really good
> current limiting in the output stage.
> Running a higher-than-rated impedance is
> just fine...you get less power output,
> of course, but the amp will run cooler
> and last longer. You can run a SS amp
> into an open circuit 'til the cows come
> home, and it won't do jack shit to it.
> Run a tube amp into an open, and you'll
> probably arc a socket (or worse) with the
> first note you play. It's a really common
> failure; I do three or four a week, year
> in, year out. So Sayeth the Lord.
I was told by a tech that there is one exception to the SS rule and that's if
the output uses MOSFET transistors... true?
Steve
Quick346
EXACTLY the info I needed, in terms anyone could understand:
With tube gear it's better to have the speaker impedance lower. Connecting a 4
ohm load to an 8 ohm amp may be OK, but connecting a 16 ohm load to an 8 ohm
amp is probably not. Connecting a 16 ohm load to a 4 ohm or 2 ohm amp is
begging to destroy the amp. Running too high of a load on tube gear can fry
anything (and occasionally everything) in the outputs, including tubes,
transformers, resistors and tube sockets.
With solid state gear it's better to run a higher impedance. Connecting an 8
ohm load to a 4 ohm amp should be fine. Running too low of a load with solid
state will fry your output transistors, and possibly more.
Danny Russell
>
> No, No. Lower load than rated output impedance is *preferable* to higher
> load than rated output impedance (amplifiers with tube output stages and
> an output transformer, such as the Fender amp referenced as the origin
> of this thread.)
>
> *Preferable* for criteria as Lord Valve has mentioned; mismatched
> impedance is still 'bad', and transformers/designs that aren't 'robust'
> (I hate that 'new' word) won't take it.
>
> The Fender in question falls into the 'usually robust enough' category.
Bob, "lesser of two evils" would be my choice of words, as neither is
preferable to a proper load match. -Danny
--
<<<GET BLITZED!!!>>>
http://home.flash.net/~blitz/tunes.html
AMD450- MIDI- MIC-&-BALLS!
Lord Valve
Simply Steve wrote:
Exception to which rule? Current is current...as the load
Z approaches zero (a short) the current approaches
infinity. Bipolar or Mosfet, smoke = smoke. As for
running unloaded (open), Mosfets are subject to gate
damage by electrostatic discharge ("static" electricity)
so there may be some truth to that rumor, although most
modern Mosfets have gate-protection diodes built
right into the package. Early Ashly power amps shipped
with shorting strips across the output binding posts, to
prevent output device damage due to static charge
buildup in packing materials; they don't come that
way any more, though. Maybe someone who knows
more about sand than I do can clear this up for us.
LV
Danny Russell
>
> Lord Valve Speaketh:
> Actually, this thread pops up every month
> or so. It always winds up the same way,
> too...the guys who know their shit tell
> everyone that it's not a good idea to run
> a tube amp at a higher load impedance
> than it's looking for, and a bunch of
> other dudes chime in with "Oh Yeah? I
> ran my (whatever) into a 16-ohm cabinet
> for years and it was rated for 8 ohms.
> What about that?"
Right on. Some people confuse dumb luck with prudence. That's no
maker of benchmarks, excepting that of stupidity. I knew a fellow who
routinely ran his car low on oil and somehow never managed to blow the
engine. Well, he's a dumbass. This is a ripe topic for aga FAQ,
including Valve's previous post. -Danny
Miles O'Neal
> This is a ripe topic for aga FAQ,
> including Valve's previous post. -Danny
It's there as of yesterdat, thank you very much. 8^)
But I am thinking of putting LV's post in there, too.
-Miles
Miles O'Neal
> I don't understand. What you're saying is completely opposite of
> anything I've ever heard before. Not that I'm doubting you, I'm sure
> you're right. I'm confused and sorry if I misled anyone.
It's pretty common. For some reason the backwards version
is "common knowledge" - even though it's wrong. I grew
up on tubes, but my best friend in college, a brilliant EE
who'd never even seen a tube up close, was always trying
to convince me that tubes like a higher impedance and SS
gear liked a lower one.
I suggested that if he really believed this, he should
try a direct short across his SS stereo output and I'd
try one across my tube tape deck outputs, but he wasn't
*that* sure. Yet he woyuldn't quit arguing with me,
until he finally got it in a course he took.
-Miles
Miles O'Neal
>
> Yup, read the FAQ (stupid me should have read that first, but no.....)
Actually, while this one has *needed* to be in there from the beginning
(what - a couple of weeks ago?) it only went in as a result of your
question and the discussion that followed. I just don't have the time
to do all that needs to be done on the site, and we still don't have the
FAQ maintainers we need.
> and got
> EXACTLY the info I needed, in terms anyone could understand:
Well, thanks. I worked hard to clarify that one.
-Miles
cjt&trefoil
transformers, so are more akin to transistor amps on this issue.
The tech in question might have had in mind that MOSFETs in some respect
behave more like tubes than transistors (i.e. gate more analogous to grid
than to base).
A good amp should be protected against thermal runaway, anyway.
JMHO. I've been wrong before.
cjt&trefoil
impedance" devices, compared to "low impedance" transistors. But that
relates to a different issue.
Miles O'Neal
>
> In defense of your friend, I believe tubes are often thought of as "high
> impedance" devices, compared to "low impedance" transistors. But that
> relates to a different issue.
No, he was just sure that he'd read and been told that
transistor gear would fry with high impedance loads,
and tubes were backwards to that.
Most of his interest was in AC power transmission, RF and
computers, so he'd never really looked into the issue.
-Miles
Quick346
>Actually, while this one has *needed* to be in there from the beginning
>(what - a couple of weeks ago?) it only went in as a result of your
>question and the discussion that followed.
Whew, okay. Didn't think I saw it when looked once before. In any case,
thanks very much!
Jack A. Zucker
This is the thread from hell! Can't we talk about something important like
digital modeling?
Happy Holidays you guys! :-)
--
Jack A. Zucker
E-Mail: j...@jackzucker.com
Jazz Guitar Page: http://www.jackzucker.com
John A. Buffaloe
speaker for a Line 21 Phod Quantum Super Linear MOSFET Heater Biased
Ultimate Overdrive Quackulator? My 8 ohm speaker sounds bad through this.
"Jack A. Zucker" <j...@gwis.com> wrote in message
news:5m826.173083$DG3.3...@news2.giganews.com...
Danny Russell
Miles O'Neal wrote:
>
> It's there as of yesterdat, thank you very much. 8^)
> But I am thinking of putting LV's post in there, too.
A nice photo collection of arced sockets would be nice (for the
disbelievers and thick skulls). I hate doing the "crass 'ol ass"
routine, but I'm continually amazed at the guitaring public's
willingness to pick up and endear themselves to fads and buzzwords
(like RECTOOFIER), yet be so resistant to the salient and proven fact
that it is potentially damaging to a tube amp to drive it hard into a
mismatched load (especially an upward mismatch). What's the problem
folks? -Danny
Miles O'Neal
>
> Does anyone have a good suggestion for a 4 ohm digital modeling replacement
> speaker for a Line 21 Phod Quantum Super Linear MOSFET Heater Biased
> Ultimate Overdrive Quackulator? My 8 ohm speaker sounds bad through this.
That's because it's analog. You need a digital speaker, or at
least a digital-ready speaker. I thnik Jack Zucker stocks the
latter, but you have to get the former from a vintage digital
dealer.
Make sure you use vintage digital solder, too, or it will never
sound right.
-M
Miles O'Neal
> A nice photo collection of arced sockets would be nice (for the
> disbelievers and thick skulls).
5 to 1 Rich posts a URL to this withino 24 hours. 8^)
>I hate doing the "crass 'ol ass"
> routine, but I'm continually amazed at the guitaring public's
> willingness to pick up and endear themselves to fads and buzzwords
> (like RECTOOFIER), yet be so resistant to the salient and proven fact
> that it is potentially damaging to a tube amp to drive it hard into a
> mismatched load (especially an upward mismatch). What's the problem
> folks? -Danny
The problem is that critical thinking and real education have
been given shorter and shorter shrift over the years, to the
point that a scary percentage of people believe anything they
are told. And authoritative information menas you heard it
from at least three people, or on the television.
-Miles
PMG
I had some digital solder once, but it only lasted for 2 connections,
then my Weller OS rebooted, it was like frying bacon without a shirt on.
Pete
--
I've been shoved off better doorsteps than yours,
I can assure you --Mr. Natural
Sent via Deja.com
http://www.deja.com/
Miles O'Neal
> > Make sure you use vintage digital solder, too, or it will never
> > sound right.
Post of the week, right there.
-Miles
--
``There ain't no good in an evil hearted woman
And I ain't cut out to be no Jesse James
And you don't go writing hot checks down in Missippi
And there ain't no good chain gang''
-Johnny Cash and Waylon Jennings
Scott Colborn
AOCrowley wrote in message ...
(snip)
. Recently I stumbled on a site called http://www.earthfiles.com
> that has some pretty odd pictures of mutilated cattle in Upstate NY/
> Toronto area. AFAIK, we havn't had a whole lot of this kind of
> thing around here, but maybe some of you folks out west are more
> familiar with this kind of thing.
>
> Anyone want to posit some theories of what's/who's doing this?
>
> -AOCrowley
Hello AOCrowley,
Check this article out:
http://www.paranormalnews.com/article.asp?ArticleID=91 . There is a short
lead-in paragraph and then scroll down the post to find the bulk of the
article on new evidence regarding bovine incisions. The subject of animal
mutilations will draw a variety of responses, ranging from
not-so-thinly-veiled ignorance to close-minded intolerance. Most of the
regular readers of this NG know me as a guitar player; some know me as a
guitar teacher, and fewer yet know of my other "hats" I wear. I host a
radio program called "Exploring Unexplained Phenomena" - in it's 17th year
now, every Saturday morning from 10 - 11 am Central Time.
Over the years I've interviewed people from all over the world on a
variety of paranormal topics, including animal mutilations. Linda Moulton
Howe is arguably one of the world's experts on this subject - she wrote "An
Alien Harvest" and produced an Emmy award-winning documentary called "A
Strange Harvest (on video now)," on the animal mutilation phenomenon. Tom
Adams of Paris, Texas is another expert....Dr. John Altschuler (pathologist)
of Colorado, Nancy Talbot of the BLT Research Team doing lab workups on
animal mute samples - see the above referenced article, etc.
Secret military testing, privately financed groups, predators,
satanists, rustlers, aliens.....theories abound. Personally I am convinced
by the data I've reviewed and the people I've personally interviewed (guests
and farm families on whose property mutilated cows and bulls were found)
that the alien connection and the secret military covert actions forces are
probably responsible.
Several e-mailed newsletters I subscribe to have occasional reports on
this subject, among them being: www.caus.org and www.filersfiles.com . As
I've stated above, I've interviewed and taken reports from families on whose
property cattle were found mutilated, sometimes under very strange
conditions. A "typical" bovine mute will have little if any blood in the
carcass, almost none on the ground around where the animal is found,
predators and farm dogs will shy away from the carcass and not mess with it
for a long time, and surrounding grass, weeds, and fauna will show almost no
trace of anyone passing through to or from the carcass. A number of cases
almost dictate that the carcass was brought back to the field and either
placed there from above or not-so-gently dropped from above and left.
The incisions themselves are not the mark left by predators. Talk to
any ranching or farm family and they can tell you about predators and the
damage they do. Try to tell one of these families on whose property a
mutilated cow was found that it was the work of predators and you better be
stepping back as you say it, cause they will call you on it real quick.
Laboratory analysis have shown in some cases that the edges of the "cuts"
are like what a laser does, not the jagged edged tears and rips of a
predator, nor is the "cuts" and incisions similiar to those of a sharp
knife. The areas of the excised flesh and hide (primarily the mouth, lips,
tongue and the anus and sexual organs) cause me to wonder about someone or
something being very interested in what the animal eats and how it
eliminates - perhaps showing concern over the food chain, etc.
Satanists and thrill-seekers have been discounted years ago for an
absolute lack of evidence. There is some evidence linking black helicopters
to areas of animal mutes (see the work of Tom Adams, Paris Texas). Also
some evidence points to the UFO phenomena as being a primary connection to
the animal mute mystery.
Thanks to Dr. W.C. Levengood, John Burke, Nancy Talbot (BLT Research
Team), Linda Moulton Howe, Tom Adams and others, we are learning more about
this mystery. Hard science and lab work have shown that there is a real
phenomenon taking place, and only under the gentle blanket of ignorance can
we hide from the implications. We have a lot more to learn, and it takes
prompt reports so that we can get people out into the fields to the animal,
and more academics to join the scientific work.
That there is a mystery I am firmly convinced. Because we can't
adequately explain cattle mutilations doesn't mean that they aren't
occuring - they have been since the mid 70's. Part of the problem has been
a bottle-neck in the upstream news flow. Many of the reports I've received
and read come from small-town newspapers that covered the initial story and
a follow-up several days later. In most cases the AP and UPI elected to not
send this story upstream and the state or regional papers then didn't cover
it, so the "story" was confined to a very small readership. Lucius Farrish
of Plumerville, Arkansas, puts out a "UFO Newsclipping Service" publication
every month, consisting of primarily smaller-town articles and stories, some
of which are on the cattle mute mystery. I subscribed to this for years and
was amazed at the number of reports (under the "large" umbrella of the
paranormal) that I read and that virtually none of them were picked up by
larger newspapers or by any of the big TV networks. Of course the idea of a
"free press" is for another post.
The two e-mailed newsletters I mentioned above will begin to give you a
sense of some highly strange events taking place all over the world, as will
Mr. Farrish's publication. My radio program is not presently on the
internet, but when and if we get it on the net, I'll put up a post to let
you folks know (grin).
Finally, I'll leave you with a short quip from the parapsychologist
Andrew Nehr, who said "It's important to keep your mind open, but not so
open that your brains fall out." Here's to open minds everywhere (and of
course tube amps)!
Walk in Beauty, Peace. Scott
Robert Graf
its output, unless the amp was class a. The Phasen Linear amps that Bob
Carver designed a couple of decades ago were class a and I've heard they
blow up without a load.
"Simply Steve" <niel...@teleport.com> wrote in message
news:3A48C831...@teleport.com...
John A. Buffaloe
come with any instructions though.
simply...@my-deja.com
Lord Valve <detr...@ix.netcom.com> wrote:
> Exception to which rule?
About running the SS output into no load being ok. This guy said that
was a definite no-no for mosfet outputs.
Steve
sco...@fundsxpress.com
>
>Ok, so now half of you are saying it's ok and the other half are saying it's
>bad?
>
>Here's some more stats:
>
>Fender tube head from the mid 60's, not sure which model, haven't seen it yet,
>he just got it and said it's a 4 ohm version.
>
Open up the cabinet and rewire it to 4 ohms... very simple, parallel
them all together (observe phasing).
This means take the old wire off the speakers, connect all the +'s
together, connect all the -'s together, then connect one speaker to
the jack. 4 ohms. 'Nuff said.
__
Steve
.
sco...@fundsxpress.com
>Why not just rewire the cabinet for 4 ohms? If it is currently 16 ohms then
>it probably has (4) 4 ohm speakers wired in series. Just rewire the
Nope... I've never seen a 16 ohm cab in that config. All Marshall
4x12s (and all others that I know of) use parallel connections with
4x16 (sometimes 15!) ohm speakers to get 4 ohms. Series connection is
bad like the old Xmas bulb strings... one goes open, you lose the
string. Better to rewire the cab to 4... see my earlier post.
__
Steve
.
Quick346
>4x12s (and all others that I know of) use parallel connections with
>4x16 (sometimes 15!) ohm speakers to get 4 ohms.
Well, I've seen his cabinet (he's had it for years) and it clearly states 300
watts/16 ohms on the back of it...
Series connection is
>bad like the old Xmas bulb strings... one goes open, you lose the
>string. Better to rewire the cab to 4... see my earlier post.
>__
>Steve
>.
No can do, then it won't work with his other head. It's six of one, half a
dozen of another...
Odin
> >Why not just rewire the cabinet for 4 ohms? If it is currently 16 ohms
then
> >it probably has (4) 4 ohm speakers wired in series. Just rewire the
>
> Nope... I've never seen a 16 ohm cab in that config.
Well that's what the poster said - 16 ohms, so that was what I was going on.
> All Marshall
> 4x12s (and all others that I know of) use parallel connections with
> 4x16 (sometimes 15!) ohm speakers to get 4 ohms.
There are no 15 ohm Celestions. Maybe you measured 15 ohms of DC
resistance, but the speaker was not a 15 ohm speaker.
> Series connection is
> bad like the old Xmas bulb strings... one goes open, you lose the
> string. Better to rewire the cab to 4... see my earlier post.
My scenario was not series, it was series/parallel. If you opened the voice
coil on one speaker you would still have at least two speakers playing.
Gary Gerhart
Odin wrote:
>
>
> There are no 15 ohm Celestions. Maybe you measured 15 ohms of DC
> resistance, but the speaker was not a 15 ohm speaker.
>
Yes, Celestion did make 15 ohm speakers!
One of my all time favorites G12-65 was available in 8 and 15 ohm configuration.
IIRC, lots of the Rola-Celestion speakers from that era were...
Gary Gerhart
Robert M. Braught
> Bob, "lesser of two evils" would be my choice of words, as neither is
> preferable to a proper load match. -Danny
Quite; would I "prefer" to prematurely waste a good set of tubes, or
potentially flash a good output transformer?
Just fixed another 'The Twin' today, set on 8 into 16; those 1/4 watt 1
ohm cathode resistors do come in handy!
Cheers,
-Robert
Lord Valve
sco...@fundsxpress.com wrote:
Wrong. Almost every Marshall 412 cab is 16 ohms stock from the
factory, using four 16-ohm speakers in series-parallel configuration.
There are exceptions, for the solid-state part of the Marshall
line...these are 8 ohms, again, using four 8-ohm drivers in
series-parallel configuration. *Very* few 412 boxes built for
tube amps are 4 ohms.
LV
cjt&trefoil
Miles O'Neal wrote:
>
<snip>
cjt&trefoil
<snip>
Series connection is
> bad like the old Xmas bulb strings... one goes open, you lose the
> string.
OTOH ...
If they're in parallel, and one blows because of an overload,
chances are the others will pop, too. If they're in series,
the first one to pop will act as a fuse.
Miles O'Neal
>
> I hear Monster Solder is good. <g>
That's what I heard. But I got some where they put it on
the roll wrong end first. You have to get that stuff
going the right direction!
Robert M. Braught
>
> John A. Buffaloe wrote:
> >
> > Does anyone have a good suggestion for a 4 ohm digital modeling replacement
> > speaker for a Line 21 Phod Quantum Super Linear MOSFET Heater Biased
> > Ultimate Overdrive Quackulator? My 8 ohm speaker sounds bad through this.
>
> That's because it's analog. You need a digital speaker, or at
> least a digital-ready speaker.
As I'm sure you're aware of, a digital speaker is a solenoid; rather
than buy new, I have great success retrofitting car door lock solenoids
(vintage 60's, GM product works best, local junk yard) when someone
wants digital speaker performance.
-Trebor
Tom
I'm curious...I've always seen the 1-ohm cathode resistors mentioned as
needing to be be rated at least 1-watt. Does anyone know what the
expected lifespan of 1/4 watters used this way is going to be? Like I
said, just curious.
Regards.
jh
cjt&trefoil schrieb:
schnipp
>
> OTOH ...
>
> If they're in parallel, and one blows because of an overload,
> chances are the others will pop, too. If they're in series,
> the first one to pop will act as a fuse.
..... reflects an open circuit to the outputstage and your tubes, the OT
and the tube sockets go kaboom with a nice flash called arcing.....
(remember your playing at full volume when you blow the voicecoil of a
speaker..)
that愀 not the kind of fuse i悲 like to have
regards
Jochen
Robert M. Braught
> > I was told by a tech that there is one exception to the SS rule and that's if
> > the output uses MOSFET transistors... true?
> >
> > Steve
>
> Exception to which rule? Current is current...as the load
> Z approaches zero (a short) the current approaches
> infinity. Bipolar or Mosfet, smoke = smoke.
> Maybe someone who knows
> more about sand than I do can clear this up for us.
> LV
I don't believe I know 'more' than you, LV, but I can relate my
experience with FET output circuits over the years-
Very early implementations (Sony, high end audiophile, ~30 years ago)
were *extremely* touchy; couldn't be brought up on a variac without
blowing up, couldn't be operated with signal if a proper load wasn't
connected or they would blow up, etc, etc. All inadequacies of the
surrounding circuit design. Plus they were using depletion mode devices,
acting like tubes that have to have their pinch off (bias) voltage
present or they would conduct full on.
All the later stuff, Hafler on, hasn't had the problems associated with
the early designs; (now using enhancement mode devices) no load and/or
low supply voltages = no immediate self-destruct problem.
Don't know of any 'late model' (<20years old) popular pieces that use
output coupling caps. Early designs didn't have any significant safety
margin for drain-to-source breakdown voltage on their devices, so
connecting a load to an output coupling cap *while the amp was on* was a
crap shoot (reverse discharging the cap at connection.), again depending
on the circuit design.
My 2c-
-Robert
Robert M. Braught
>
> I can't think of a reason why a mosfet amp wouldn't like an open circuit on
> its output, unless the amp was class a. The Phasen Linear amps that Bob
> Carver designed a couple of decades ago were class a and I've heard they
> blow up without a load.
'Flame Linear' 400's will blow up depending on the phase of the moon!
-Robert
John A. Buffaloe
than buy new, I have great success retrofitting car door lock solenoids
(vintage 60's, GM product works best, local junk yard) when someone
wants digital speaker performance.
-Trebor
But wouldn't a car door lock solenoid be inherently noisy thus defeating the
purpose and function of true digital speaker function? Could this be
corrected by additional Nyquist filtering? And if it's the GM product that
works best, and if it's specifically Oldsmobile, is there some way to
compensate for say, a Buick version in several years when Oldsmobile is no
more?
Robert M. Braught
>
> Bob:
>
> I'm curious...I've always seen the 1-ohm cathode resistors mentioned as
> needing to be be rated at least 1-watt. Does anyone know what the
> expected lifespan of 1/4 watters used this way is going to be? Like I
> said, just curious.
This came up on another thread recently; ohms/watts law stuff; it works
out that you'd have to have 0.5 volts across your 1 ohm resistor to get
to 1/4 watt, which translates to 500 ma(!) -going through your tube(s)
cathode(s).
So the answer, in a practical sense, is "until failure of something
else."
'The Twin' uses one 1/4w resistor on each phase pair of output tubes,
and in my experience they often act as fuses for a shorted output tube
(I only wish they'd have either used flame-proof resistors, or bent them
up off the board, to prevent the mess when they 'blow'.)
-Robert
Tom
Regards.
cjt&trefoil
jh
Jochen
cjt&trefoil schrieb:
Lord Valve
and SCS (BARF!!) so stuff from the audiophool
sphere is mostly outside my experience. The
Ashly amps have a reputation for being the
most bulletproof amps ever designed for
pro use. They weigh a ton, too. :-) The Hafler
Pro stuff was good, but not as tough as the
Ashly. SCS (Sound Code Systems) built
some of the rottenest "pro" gear I've ever
encountered...and they were a bitch to work
on, too. If you ever run across one, strip the
K & J series TO-3 Mosfets out of it and pitch
the rest into the shitcan.
LV
Robert M. Braught
-Robert
Rich Koerner
Scott Colborn wrote:
>
> AOCrowley wrote in message ...
>
> (snip)
>
> . Recently I stumbled on a site called http://www.earthfiles.com
> > that has some pretty odd pictures of mutilated cattle in Upstate NY/
> > Toronto area. AFAIK, we havn't had a whole lot of this kind of
> > thing around here, but maybe some of you folks out west are more
> > familiar with this kind of thing.
> >
> > Anyone want to posit some theories of what's/who's doing this?
> >
> > -AOCrowley
>
> Hello AOCrowley,
> Check this article out:
> http://www.paranormalnews.com/article.asp?ArticleID=91 . There is a short
> lead-in paragraph and then scroll down the post to find the bulk of the
> article on new evidence regarding bovine incisions. The subject of animal
> mutilations will draw a variety of responses, ranging from
> not-so-thinly-veiled ignorance to close-minded intolerance. Most of the
> regular readers of this NG know me as a guitar player; some know me as a
> guitar teacher, and fewer yet know of my other "hats" I wear. I host a
> radio program called "Exploring Unexplained Phenomena" - in it's 17th year
> now, every Saturday morning from 10 - 11 am Central Time.
> Over the years I've interviewed people from all over the world on a
> variety of paranormal topics, including animal mutilations. Linda Moulton
> Howe is arguably one of the world's experts on this subject - she wrote "An
> Alien Harvest" and produced an Emmy award-winning documentary called "A
> Strange Harvest (on video now)," on the animal mutilation phenomenon. Tom
> Adams of Paris, Texas is another expert....Dr. John Altschuler (pathologist)
> of Colorado, Nancy Talbot of the BLT Research Team doing lab workups on
> animal mute samples - see the above referenced article, etc.
> Secret military testing, privately financed groups, predators,
> satanists, rustlers, aliens.....theories abound. Personally I am convinced
> by the data I've reviewed and the people I've personally interviewed (guests
> and farm families on whose property mutilated cows and bulls were found)
> that the alien connection and the secret military covert actions forces are
> probably responsible.
> Several e-mailed newsletters I subscribe to have occasional reports on
> this subject, among them being: www.caus.org and www.filersfiles.com . As
> I've stated above, I've interviewed and taken reports from families on whose
> property cattle were found mutilated, sometimes under very strange
> conditions. A "typical" bovine mute will have little if any blood in the
> carcass, almost none on the ground around where the animal is found,
> predators and farm dogs will shy away from the carcass and not mess with it
> for a long time, and surrounding grass, weeds, and fauna will show almost no
> trace of anyone passing through to or from the carcass. A number of cases
> almost dictate that the carcass was brought back to the field and either
> placed there from above or not-so-gently dropped from above and left.
> The incisions themselves are not the mark left by predators. Talk to
> any ranching or farm family and they can tell you about predators and the
> damage they do. Try to tell one of these families on whose property a
> mutilated cow was found that it was the work of predators and you better be
> stepping back as you say it, cause they will call you on it real quick.
> Laboratory analysis have shown in some cases that the edges of the "cuts"
> are like what a laser does, not the jagged edged tears and rips of a
> predator, nor is the "cuts" and incisions similiar to those of a sharp
> knife. The areas of the excised flesh and hide (primarily the mouth, lips,
> tongue and the anus and sexual organs) cause me to wonder about someone or
> something being very interested in what the animal eats and how it
> eliminates - perhaps showing concern over the food chain, etc.
> Satanists and thrill-seekers have been discounted years ago for an
> absolute lack of evidence. There is some evidence linking black helicopters
> to areas of animal mutes (see the work of Tom Adams, Paris Texas). Also
> some evidence points to the UFO phenomena as being a primary connection to
> the animal mute mystery.
> Thanks to Dr. W.C. Levengood, John Burke, Nancy Talbot (BLT Research
> Team), Linda Moulton Howe, Tom Adams and others, we are learning more about
> this mystery. Hard science and lab work have shown that there is a real
> phenomenon taking place, and only under the gentle blanket of ignorance can
> we hide from the implications. We have a lot more to learn, and it takes
> prompt reports so that we can get people out into the fields to the animal,
> and more academics to join the scientific work.
> That there is a mystery I am firmly convinced. Because we can't
> adequately explain cattle mutilations doesn't mean that they aren't
> occuring - they have been since the mid 70's.
Nothing previous to this point in time?????
Interesting!!!!!!
Is this a global affair, or just a USA thing????
What of Canada, Mexico, or England????
Is there a connection to the Mad Cow situation now before us????
> Part of the problem has been
> a bottle-neck in the upstream news flow. Many of the reports I've received
> and read come from small-town newspapers that covered the initial story and
> a follow-up several days later. In most cases the AP and UPI elected to not
> send this story upstream and the state or regional papers then didn't cover
> it, so the "story" was confined to a very small readership. Lucius Farrish
> of Plumerville, Arkansas, puts out a "UFO Newsclipping Service" publication
> every month, consisting of primarily smaller-town articles and stories, some
> of which are on the cattle mute mystery. I subscribed to this for years and
> was amazed at the number of reports (under the "large" umbrella of the
> paranormal) that I read and that virtually none of them were picked up by
> larger newspapers or by any of the big TV networks. Of course the idea of a
> "free press" is for another post.
> The two e-mailed newsletters I mentioned above will begin to give you a
> sense of some highly strange events taking place all over the world, as will
> Mr. Farrish's publication. My radio program is not presently on the
> internet, but when and if we get it on the net, I'll put up a post to let
> you folks know (grin).
> Finally, I'll leave you with a short quip from the parapsychologist
> Andrew Nehr, who said "It's important to keep your mind open, but not so
> open that your brains fall out." Here's to open minds everywhere (and of
> course tube amps)!
> Walk in Beauty, Peace. Scott
Regards,
Rich Koerner,
Time Electronics.
http://www.timeelect.com
Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers
Dave Moore
Lord Valve <detr...@ix.netcom.com> wrote in message
news:3A47C210...@ix.netcom.com...
> TB1000 wrote:
>
> >You got got that completely wrong.
> LV: No, he didn't, and that means you get an LV
> online ass-whuppin' fer Christmas.
>
> >It's dangerous to tube amps to use speakers with
> >ratings less than the output of the amp.
> LV: No, it isn't...unless the output stage runs
> triodes. Most guitar amps don't.
>
> >It's safe to use a 16 ohm cab with a 4 ohm amp.
> LV: No, it isn't. You can refer to the repost of
> Ken Gilbert's excellent explanation (earlier
> on this thread) if you want the technical
> mojo, but in a nutshell a pentode output stage
> that's driving an upward mismatch is prone to
> flyback, which can cause arced sockets, popped
> HV capacitors, punctured insulation on wiring,
> and even primary-to-core shorts in the OPT.
> Don't do it.
I don' think it was an excellent explanation at'all. More like
a gross exageration. What Kenny described was what would happen
if a transformer coupled ouput amplifier was run with *no load at all*.
The origional poster did not ask that. From my experience, running
a 4 ohm amp at 16 ohms only increases the primary voltage in
the neighborhood of 100 to 200 volts. That's hardly Kenny's vision
of flyback apocalypse!!! Two things at work here. In the first place,
the voltage across the windings of the output transformer is distributed
across the layers of windings. Therefore, the additional 100-200 volts
has to be divided by the number of layers to determine what increase
in voltage any particular layer would see. The xtra 100-200 volts
divided by a number of layers doesn't really result in that much of an
increase per layer. This is not much stress for the tranny.
Most transformer designers design for twice the working voltage
+ an additional 1 thousand volts margin. So you can see that in normal
operation, running a 4 ohm amp into a 16 ohm load isn't likely to fry
the output transformer. But before the flames fly, notice that I said
"in normal operation". By normal operation, I mean linear,clean,
no distortion or clipping. Once you clip the holy hell out of the output
section, as some rock and rollers are sometimes compelled to do,
the ouput section starts to look more like a switch mode power supply.
That's when the inductive shit hits the fan so to speak. However, it's
still not as bad as the *no load* scenario that Kenny described.
With the 16 ohm load the inductive peaks are still within the 100 -200
volt range. However a new phenomena enters the picture.
When you pulse a transformer, due to the inductive nature of the
transformer, the voltage under these conditions is *not* evenly
distributed throughout the winding layers of the transformer.
Therefore higher voltages can develop in certain areas of the
transformer than would occur for linear (undistorted) operation.
Whether the tranny can handle this?
Only his tranny designer knows for sure !!!!
IMHO more than likely it'll hold up, but I wouldn't do it with
my tranny ;-)
With 16 ohms, there is still at least somewhere for most of the
energy to go, so the flyback scenario isn't as bad as all that
with a mismatch as it would be from a *no load* condition.
=^^= DM
> Lord Valve
>
> VISIT MY WEBSITE: http://www.nebsnow.com/LordValve
> I specialize in top quality HAND SELECTED NOS and
> current-production vacuum tubes for guitar and
> bass amps. Good prices, fast service.
>
> NBS Electronics, 230 South Broadway, Denver, CO 80209-1510
> Phone orders/tech support after 1:30 PM Denver time at 303-778-1156
>
> VISA - MASTERCARD
Dave Moore
(see my other post in this thread) =^^= DM
Miles O'Neal <m...@rru.com> wrote in message news:3A48EF37...@rru.com...
> Danny Russell wrote:
> > This is a ripe topic for aga FAQ,
> > including Valve's previous post. -Danny
>
> It's there as of yesterdat, thank you very much. 8^)
> But I am thinking of putting LV's post in there, too.
>
> -Miles
Miles O'Neal
>
> Probably so, but y'all might want to get you FAQ's straight first.
> (see my other post in this thread) =^^= DM
Your post was for "properly designed transformers".
Perhaps today's amps use such things (anyone know?)
but the majority of tube guitar amps built, at least
during the Golden Age, used whatever they could get
that they could afford. A lot of the best tube amps
actually had marginal trannies if played loudly. Esp.
if the guitarist overdrove the amp hard. Fouling up
the impedance equation would push them over the edge
for sure.
-Miles
Lord Valve
Dave Moore wrote:
Fried sockets on Marshalls from setting the selector
to 4 ohms and connecting a 16 ohm cabinet are rampant.
I'd say one out of ten of these, the tranny is fried too.
Remember, this is a *guitar* amp NG...and guitar amps
are routinely operated beyond "linear." In fact, that's
the whole point of using a tube amp.
LV
Jim McShane
> > > >It's safe to use a 16 ohm cab with a 4 ohm amp.
Lord Valve then wrote...
> > > LV: No, it isn't. You can refer to the repost of
> > > Ken Gilbert's excellent explanation (earlier
> > > on this thread) if you want the technical
> > > mojo, but in a nutshell a pentode output stage
> > > that's driving an upward mismatch is prone to
> > > flyback, which can cause arced sockets, popped
> > > HV capacitors, punctured insulation on wiring,
> > > and even primary-to-core shorts in the OPT.
> > > Don't do it.
This was a lesson for me too when I began to get interested
in musical instrument amps. Audio-wanker that I am, I routinely
played games with mismatched impedances, etc. changing the
load on the output tubes (remember the primary impedance
of an OPT is a function of reflected secondary load and turns
ratios). In audio gear, it's no big deal. In instrument amps it's
a BIG deal.
LV set me straight on that long ago when he explained the height
of the pile of output tube sockets he changed due to arcing! It's
virtually unheard of in audio gear, but not in heavily used musical
instrument amps.
FWIW.
Jim McShane
Need NOS or New Tubes? Got a H-K Citation (Pre) Amp?
See my web pages at http://pages.prodigy.net/jimmcshane
cjt&trefoil
It sounds like guitar amps cry out for ceramic tube sockets.
Danny Russell
Jim McShane wrote:
>
> This was a lesson for me too when I began to get interested
> in musical instrument amps. Audio-wanker that I am, I routinely
> played games with mismatched impedances, etc. changing the
> load on the output tubes (remember the primary impedance
> of an OPT is a function of reflected secondary load and turns
> ratios). In audio gear, it's no big deal. In instrument amps it's
> a BIG deal.
>
> LV set me straight on that long ago when he explained the height
> of the pile of output tube sockets he changed due to arcing! It's
> virtually unheard of in audio gear, but not in heavily used musical
> instrument amps.
This is right on. Hi-Fi cats will set the impedance selector one
notch off in either direction if it happens to sound better set that
way. At low to moderate levels, no harm, no foul. With an overdriven
output section (read guitar amps), all bets are out the window.
I'm going to post everytime I complete a repair to an amp's output
circuit belonging to an impedance indifferent player. -Danny
--
<<<GET BLITZED!!!>>>
http://home.flash.net/~blitz/tunes.html
AMD450- MIDI- MIC-&-BALLS!
Chris Mohrbacher
"cjt&trefoil" <chel...@prodigy.net> wrote in message
news:3A4E56EA...@prodigy.net...
I've got a Sovtek Mig 100 that came with ceramic sockets, and it has a pair
of 390pf capacitors rated at 2000 volts connected across two of the output
sockets. I guess they figure it's better to arc through a (fairly) cheap
capacitor rather than transformer insulation.
--- Chris
Steve
I will try to demo and upload samples from my 60s Kustom 100 combo, which has trem & uibrato. And scratchy pots ....
Don't Spam <DontSpam...@earthlink.net> wrote:
__________
>In article <3A4D6E70...@rru.com>, m...@rru.com says...
>> Mike Schway wrote:
>>
>> > Check this:
>> >
>> > http://www.teleport.com/~vibroman/magnatone/vibrato.html
>>
>> I've seen this. It's what prompted me to try to
>> talk with the Magnatone site guy to begin with.
>> But I've looked over a bunch of schematics, and
>> I have yet to see anything that vaguely looks like
>> it could produce real pitch vibrato.
>>
>> There's nothing special about varistors. There are
>> a lot of things you can do with them. And I've yet
>> to figure out how *any* of the magnatone circuits
>> can produce a real vibrato.
>>
>> Having said that...
>>
>> 1) Does anyone on this NG own a vibrato, or have access to
>> one, who can perhaps make sound samples available? I
>> don;t want something fancy, I want something so simple
>> it's obvious what we're hearing. Set the vibrato to a
>> speed where we can clearly hear the pitch change (if any).
>> Play a single note, let it sustain as long as possible.
>> Play chords, same thing. Then, if you want to show what
>> your chops and a Magnatone sound like together, that's
>> great, but let's get to the heart of the matter first, OK?
>> 2) Any of you with reasonable electronics knowledge, feel free
>> to pick a representative Magnatone circuit and explain the
>> theory behind how that circuit can act as a true vibrato
>> circuit.
>>
>> I am not anti-Magnatone. I simply don't see how the circuits
>> I have access to (including what I saw on the patent drawing)
>> can produce true pitch vibrato.
>>
>> I went to the USPTO site and found the patent. They don't
>> seem to be sending the correct MIME header, and loading
>> things by hand, one TIFF at a time, is a pain. Then, they're
>> kind of hard to read. So I went to order one, and their
>> "security site found a database error". Great. So, that
>> wasn't much help!
>>
>> I also searched the Magnatone forum linke dto from the Magnatone
>> site - no technical discussion of the circuit that I could
>> find.
>>
>> -Miles
>>
>I suppose, since I have both Vibrato, and Trem, AND a stereo guitar.. I
>could try to get a sample done. The only variable that I would have,
>would be this;
>one sample would be from the neck pickup, and one from the bridge pickup.
>I could possibly do 2 samples, and simply reverse the pickups for a
>second sampling.
>
>I'll think on this, and see if I'd be able to get it done correctly.
>
>Regards
Rich Koerner
Odin wrote:
>
> <sco...@fundsxpress.com> wrote in message
>
> > >Why not just rewire the cabinet for 4 ohms? If it is currently 16 ohms
> then
> > >it probably has (4) 4 ohm speakers wired in series. Just rewire the
> >
> > Nope... I've never seen a 16 ohm cab in that config.
>
> Well that's what the poster said - 16 ohms, so that was what I was going on.
>
> > All Marshall
> > 4x12s (and all others that I know of) use parallel connections with
> > 4x16 (sometimes 15!) ohm speakers to get 4 ohms.
>
> There are no 15 ohm Celestions. Maybe you measured 15 ohms of DC
> resistance, but the speaker was not a 15 ohm speaker.
Check it out!!!!
http://www.timeelect.com/test/pc310005.jpg
Rich Koerner
There are the many factors mentioned from the mis-match to the over
driven amplifier condition that resembles a switching power supply or
square wave generator.
Any of the above will give the following as a result:
http://www.timeelect.com/test/F7171459.jpg
http://www.timeelect.com/test/F7171447.jpg
Hey, I have heard the tones generated by a 2 ohm Super Reverb plugged
into a 16 ohm Marshall cab with four original green back 30's.
Yes, it's TONE heaven!!! But, THERE IS A *PRICE* TO PAY!!!!
It is best not to upset the apple cart by
applications other than what was intended
by specific engineered design!!!!
Shit happens, even when the rules are followed!!!!
Quick346
Dave Moore
news:92ljfe$jrmo$1...@newssvr06-en0.news.prodigy.com...
> In a prior post, it was written...
>
> > > > >It's safe to use a 16 ohm cab with a 4 ohm amp.
>
> Lord Valve then wrote...
>
> > > > LV: No, it isn't. You can refer to the repost of
> > > > Ken Gilbert's excellent explanation (earlier
> > > > on this thread) if you want the technical
> > > > mojo, but in a nutshell a pentode output stage
> > > > that's driving an upward mismatch is prone to
> > > > flyback, which can cause arced sockets, popped
> > > > HV capacitors, punctured insulation on wiring,
> > > > and even primary-to-core shorts in the OPT.
> > > > Don't do it.
>
> This was a lesson for me too when I began to get interested
> in musical instrument amps. Audio-wanker that I am, I routinely
> played games with mismatched impedances, etc. changing the
> load on the output tubes (remember the primary impedance
> of an OPT is a function of reflected secondary load and turns
> ratios). In audio gear, it's no big deal. In instrument amps it's
> a BIG deal.
yeah, well isn't that what I said, once you start clipping the output
it's a different story.
>
> LV set me straight on that long ago when he explained the height
> of the pile of output tube sockets he changed due to arcing! It's
> virtually unheard of in audio gear, but not in heavily used musical
> instrument amps.
Ok, but where's the proof that the arcing was due to a mismatch
and not due to someone operating no load, as often happens when
cords fail or people trip over them?
You might want to pull your scope out of mothballs
and actually look at some waveforms with a mismatched load.
I've never seen anything empirical to indicate that socket arcing
would be a problem with such a mismatch. However, my CAD
program shows spikes of over 1 thousand volts when operated
no load at all. Sorry, but the no load experiment is one that I'll
only simulate with CAD for now as I'm not yet rich enough to
to fry and toss tranny's for fun yet. ;-)
=^^= DM
Dave Moore
<snipped>
> Fried sockets on Marshalls from setting the selector
> to 4 ohms and connecting a 16 ohm cabinet are rampant.
> I'd say one out of ten of these, the tranny is fried too.
> Remember, this is a *guitar* amp NG...and guitar amps
> are routinely operated beyond "linear." In fact, that's
> the whole point of using a tube amp.
> LV
>
Well yes, that's why I said when clipping all bets are off.
Believe me, I've fried many a semiconductor driving OT's to their
extremes and beyond
However, something you're saying here doesn't add up.
First of all, have you verified with the owners of these amps that
they were using the amps with the settings correct and then suddenly
(and only) then when they set it to the mismatch the problems occured.
How do you now that they didn't use the amps like that for years
before the sockets arced.
Second thing that seems odd is that you say one in ten had fried
transformers. I would think that the sockets would have a higher
insulation resistance than the windings in the transformer. It seems
strange to me that the sockets would check out before the trannies.
I'm not doubting that you have a pile of fried sockets, I'm just trying
to take a closer look and dissect the evidence a bit, so if there is
another explanation it can be ruled out. One theorem, is it possible
that possibly since Marshalls have the chassi's on the bottom,
it makes it easier for dirt, beer, spit, and other contaminants to
get on the sockets. Combine dirt and a little humidity, and you
have a recipe for disaster. I'm not sure if a lot of tech's realize the
importance of cleaning the entire socket, and not just the contacts.
Could be that setting the speaker selector to 4 ohms and running
a 16 ohm cabinet might just be contributing to a failure that was
on the verge of happening anyway.
Another thing, that you've said that's got me curious, why not
this problem with Fenders. Although, I can see that a Marshalls
setup makes it a bit more likely to happen with a Marshall.
Another thing I'll confess to is that, I have only tested amps
for flyback up to 100W. I haven't seen anything that would
cause such damage to trannies or sockets in amps in this power
range, even when severely overdriven. However, I have no
empirical data on amps above 100W.
So let me ask, what is the power range of the Marshalls you get
in with fried sockets,
Are they typically the higher powered amps?
This is an issue that I am extremely interested in since I am
designing a flyback crowbar circuit at this time. Perhaps I'll
have to acquire some higher powered amps to abuse !!! :-)
=^^= DM
Dave Moore
True, good point.
All I'm trying to say, is before you put something in the FAQ's
look at all sides and try to get things into perspective so that
the truth be told so that myth's are not born to be perpetuated.
I still feel that Kenny's *no load* description was *mismatched*
to the question of *speaker mismatch*.
=^^= DM
Danny Russell
Dave Moore wrote:
>
> > > Probably so, but y'all might want to get you FAQ's straight first.
> > > (see my other post in this thread) =^^= DM
>
> True, good point.
> All I'm trying to say, is before you put something in the FAQ's
> look at all sides and try to get things into perspective so that
> the truth be told so that myth's are not born to be perpetuated.
> I still feel that Kenny's *no load* description was *mismatched*
> to the question of *speaker mismatch*.
> =^^= DM
Dave, you don't actually fix amps for a living do you? -Danny
Chris Mohrbacher
> designing a flyback crowbar circuit at this time.
You too, huh?!? Is it for some other use, or is it specifically for
protecting guitar amps from "no-loads"?
--- Chris
Chris Mohrbacher
"Dave Moore" <nova...@datasync.com> wrote in message
news:92odgc$moh$1...@news.datasync.com...
After I got further along with my lab experiments I was going to start a
related thread, but I can't resist jumping in here:
I have a Traynor that I'm using as a high-voltage guinea pig. When plugged
into an 8-ohm or 16-ohm load resistor, I can't create spikes of more than a
few hundred extra volts on the output transformer primary (the amp is
spec'ed for 8-ohm use). BUT when I plug it into a Marshall Powerbrake, on
the 8-ohm setting I can generate spikes of up to about 2500 volts, and on
the 16-ohm setting I can generate 5kv spikes.
The difference between the load resistor and the Powerbrake is due to a 1 mH
inductor that Marshall designed into the PB, which is there (as far as I can
tell) to simulate the inductance of the voice coils in a speaker cabinet.
(the inductance of one of my Celestion G12-M70s just happens to be 1 mH;
coincidence?) Without a load at all on Franken-Traynor, the voltage spikes
would easily go higher but right now I have an experimental crowbar circuit
which keeps them from climbing past about 5kv.
I would also like to add this; when a push-pull tube output stage is driven
into deep clipping, there are brief intervals where none of the tubes are
conducting. My hunch is that during these intervals there is effectively no
load on the primary side and therefore large voltage spikes can build up
unimpeded. I believe the voltage spikes I observe are occurring in these
intervals.
--- Chris
Lord Valve
Lord Valve <detr...@ix.netcom.com> wrote in message
news:3A4E41D5...@ix.netcom.com...
>><snipped>
>> Fried sockets on Marshalls from setting the selector
>> to 4 ohms and connecting a 16 ohm cabinet are rampant.
>> I'd say one out of ten of these, the tranny is fried too.
>> Remember, this is a *guitar* amp NG...and guitar amps
>> are routinely operated beyond "linear." In fact, that's
>> the whole point of using a tube amp.
>> LV
>>
>Well yes, that's why I said when clipping all bets are off.
>Believe me, I've fried many a semiconductor driving OT's
>to their extremes and beyond However, something you're
>saying here doesn't add up. First of all, have you
>verified with the owners of these amps that they were
>using the amps with the settings correct and then suddenly
>(and only) then when they set it to the mismatch the problems
>occured.
LV: DUDE! We're talking about *musicians* here...most of
'em are newbies, they can't tell a phase inverter from
a fire hydrant. Yeah, I'm *double damn sure* they
screwed up. Most of the time they have just acquired
the amp, don't know how it works, and didn't take
the time to find out. One thing a pro bench tech learns
*really* early is to ask *tons* of questions about how
the amp was being operated when it failed...if you don't,
sure as shit it's gonna come back in a couple of days,
fried exactly the same way. In fact, I make 'em bring
me *everything* they were using when the amp failed...
guitar, effects, cables, amp head, speaker...EVERYTHING.
>How do you now that they didn't use the amps like that
>for years before the sockets arced.
LV: I asked 'em. I've been asking 'em for 30 years.
>Second thing that seems odd is that you say one in ten had
>fried transformers. I would think that the sockets would
>have a higher insulation resistance than the windings in
>the transformer. It seems strange to me that the sockets
>would check out before the trannies.
LV: Yes, but you're a solder-sniffer, not a geetah-pickah.
Once a socket arcs, it blows the fuse. You got any
idea what a musician does when a fuse blows in the
middle of a show and he has no backup amp? What
happens is, he feeds the amp a steady diet of fuses
(sometimes, larger and larger ones...I've had 50W
Marshalls come in with 20-amp automotive fuses stuffed
into the B+ fuseholder) until the show is over. In
fact, he sometimes feeds it fuses for weeks...even
MONTHS. Every time the socket arcs, it gets more
conductive, and arcs easier the next time. I've seen
'em come in with blown trannies, popped filters, hell,
I've seen amps that *literally* caught fire...complete
with fire-extinguisher scuzz all over 'em.
>I'm not doubting that you have a pile of fried sockets,
>I'm just trying to take a closer look and dissect the
>evidence a bit, so if there is another explanation it
>can be ruled out. One theorem, is it possible that possibly
>since Marshalls have the chassi's on the bottom, it makes it
>easier for dirt, beer, spit, and other contaminants to get on
>the sockets. Combine dirt and a little humidity, and you have
>a recipe for disaster. I'm not sure if a lot of tech's realize
>the importance of cleaning the entire socket, and not just the
>contacts.
LV: Hey...you wanna lecture somebody, go find a newbie.
30 years, remember?
>Could be that setting the speaker selector to 4 ohms and
>running a 16 ohm cabinet might just be contributing to a
>failure that was on the verge of happening anyway.
LV: I've seen brand new guitar amps, two days away from
Guitar Center, fried from wrong impedance settings.
Do you have *any idea* how loud these things are
operated in thrash or punk bands?
>Another thing, that you've said that's got me curious,
>why not this problem with Fenders.
LV: Because a majority of Fenders are combo amps, used
with their internal speakers, wired correctly from the
factory. Not to mention which, few of 'em have
impedance selectors anyway. Less opportunity to
set them wrong. Most Marshalls, on the other hand,
are stacks. Ditto for Laney, Orange, Hiwatt, etc.
Nonetheless, I see plenty of toasted Fenders, too.
>Although, I can see that a Marshalls setup makes it a bit
>more likely to happen with a Marshall. Another thing I'll
>confess to is that, I have only tested amps for flyback up
>to 100W. I haven't seen anything that would cause such damage
>to trannies or sockets in amps in this power range, even when
>severely overdriven. However, I have no empirical data on amps
>above 100W. So let me ask, what is the power range of the
>Marshalls you get in with fried sockets, Are they typically
>the higher powered amps?
LV: I don't see that this condition is particularly related
to any specific power range...50-watt, 100-watt, doesn't
matter. Plenty of fried Fenders in all power classes,
too. In fact, one of the most common ones is the Champ,
a class-A runt with a single 6V6 for an output tube.
*Lots* of these come in with fried sockets...sooner or
later, the owner gets the bright idea that he may be able
to get a lot more volume out of his Champ if he plugs it
into his Marshall cabinet...4-ohm Champ, 16-ohm cabinet,
presto...fried socket. Happens *all* the time. We're
talking about a 4-5 watt practice amp, here.
>This is an issue that I am extremely interested in since I am
>designing a flyback crowbar circuit at this time. Perhaps I'll
>have to acquire some higher powered amps to abuse !!! :-)
LV: Doesn't have jack to do with power. Has everything to do
with voltage. If I recall correctly, Traynor had some
kind of fancy clamps across the OPT primary, back when
dinosaurs roamed the earth. Sometimes, they even worked.
Another trick is to series a couple of MOVs across the
primary, to clamp spikes. Never tried it, though...
it'd probably play hell with the rectifier tube, if the
amp has one.
Lord Valve
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-Ray Charles-
Miles O'Neal
>
>Someone oopsed:
>
> > There are no 15 ohm Celestions. Maybe you measured 15 ohms of DC
> > resistance, but the speaker was not a 15 ohm speaker.
>
> Check it out!!!!
>
> http://www.timeelect.com/test/pc310005.jpg
Ho. Ho. Ho.
or is that D'oh?
Miles O'Neal
> Ok, but where's the proof that the arcing was due to a mismatch
> and not due to someone operating no load, as often happens when
> cords fail or people trip over them?
> You might want to pull your scope out of mothballs
> and actually look at some waveforms with a mismatched load.
> I've never seen anything empirical to indicate that socket arcing
> would be a problem with such a mismatch. However, my CAD
> program shows spikes of over 1 thousand volts when operated
> no load at all. Sorry, but the no load experiment is one that I'll
> only simulate with CAD for now as I'm not yet rich enough to
> to fry and toss tranny's for fun yet. ;-)
You can make all the noise you want about this; the guys who
are you telling you different have seen it over and over and
over.
I just lost a socket two or three weeks ago. I thought it was
a solder problem. But it was because the speaker cab the amp
was going into was a 16 ohm cab instead of an 8 ohm cab. The
amp had been rebuilt, and I know for a fact it had *not* been
played at no load since the rebuild (complete with new output
tranny and new tubes).
A CAD program is no substitute for real world experience. It's
a good introduction to certain things, but without the experience,
that's all it is. An introductory text.
-Miles