Blackface a Silverface Super Reverb
tle4
back from Gerald Weber with the steps to convert a silverface Super Reverb
to Blackface. It is pretty simple to do with step by step onstructions if
anyone is interested that has an old silverface.
Too long in the Wasteland
Sure..
Can You scan a copy and post it ?
tle4
I dont have a scanner righ now. Guitar Player posts their Gear question
articles online but I dont know how long it will take for it to get up on
their web page
"Too long in the Wasteland" <b24wa...@gmail.com> wrote in message
news:baea4396-2836-4825...@26g2000hsk.googlegroups.com...
Lost in the Wasteland
> Sorry,
> I dont have a scanner righ now. Guitar Player posts their Gear question
> articles online but I dont know how long it will take for it to get up on
> their web page
>
*black facing* generally means removing parts ... does it mention
a particular circuit ? aa763/ab763 ?
Stephen Cowell
"Lost in the Wasteland" <Lo...@there.com> wrote in message
news:484c6f45$0$4092$bbae...@news.suddenlink.net...
Gerald doesn't tell you that these parts were
added in order to allow the more haphazard
stranded wiring you'll see in the later units.
In order to properly blackface a Fender
you need to change the wiring to solid-core
(it stays where you put it) and you have to
do the proper lead dress (get a BF and
take pictures, my buddy did this (on my
rec!) and came out smiling).
__
Steve
.
tle4
"Stephen Cowell" <sco...@sbcglobal.net> wrote in message
news:nF_2k.4966$uE5....@flpi144.ffdc.sbc.com...
It does not tell you what silverface circuit. I would guess it would be an
earlier one.
Here are the titles to the 4 steps
1. Rewire bias supply and add two 220k resistors
2. Replace 4 resistors in phase inverter
3. Remove parasitic supression caps
4. Change 5u4 rectifier tube to 5ar4/gz34 and check bias
Stephen Cowell
"tle4" <tl...@verizon.net> wrote in message
news:K7%2k.2235$1x.1372@trndny06...
>
> "Stephen Cowell" <sco...@sbcglobal.net> wrote in message
> news:nF_2k.4966$uE5....@flpi144.ffdc.sbc.com...
>>
>> "Lost in the Wasteland" <Lo...@there.com> wrote in message
>> news:484c6f45$0$4092$bbae...@news.suddenlink.net...
>>> tle4 wrote:
>>>> Sorry,
>>>> I dont have a scanner righ now. Guitar Player posts their Gear question
>>>> articles online but I dont know how long it will take for it to get up
>>>> on their web page
>>>>
>>>
>>>
>>> *black facing* generally means removing parts ... does it mention
>>> a particular circuit ? aa763/ab763 ?
>>
>> Gerald doesn't tell you that these parts were
>> added in order to allow the more haphazard
>> stranded wiring you'll see in the later units.
>>
>> In order to properly blackface a Fender
>> you need to change the wiring to solid-core
>> (it stays where you put it) and you have to
>> do the proper lead dress (get a BF and
>> take pictures, my buddy did this (on my
>> rec!) and came out smiling).
>
> earlier one.
>
> Here are the titles to the 4 steps
>
> 1. Rewire bias supply and add two 220k resistors
> 2. Replace 4 resistors in phase inverter
> 3. Remove parasitic supression caps
This is the one he's not helping with... when
you remove the caps, guess what... you'll get
parasitics.
> 4. Change 5u4 rectifier tube to 5ar4/gz34 and check bias
This puts *less* sag in the circuit, and may not
be what everyone wants. Gerald sells a lot of
books... I've been to his shop and met the man.
Nice guy... no engineer.
__
Steve
.
Dave Curtis
I add a 'level' pot to the existing 'balance' circuit. What 220K
resistors? Mine had 2 already.
>> 2. Replace 4 resistors in phase inverter
That depends. I thought it sounded better without changing them. I've
since read an article somewhere on the topic (Aiken?).
>> 3. Remove parasitic supression caps
>
>This is the one he's not helping with... when
>you remove the caps, guess what... you'll get
>parasitics.
Maybe. Maybe not.
My '76 Pro Reverb does fine without them.
>> 4. Change 5u4 rectifier tube to 5ar4/gz34 and check bias
>
>This puts *less* sag in the circuit, and may not
>be what everyone wants. Gerald sells a lot of
>books... I've been to his shop and met the man.
>Nice guy... no engineer.
>__
>Steve
>.
Gerald+ grain of salt = OK
-DC
Ether
Yes...
> 2. Replace 4 resistors in phase inverter
Yes...
> 3. Remove parasitic supression caps
Maybe...
> 4. Change 5u4 rectifier tube to 5ar4/gz34
Bad idea. The PT secondary voltage is 35 volts higher on the
silverface version. Using a 5ar4 will put the B+ and plate voltage too
high, probably more than 475 volts and maybe up closer to 500. Unless
you're willing to change the PT, keep the 5U4.
> and check bias
Always.
--E
Rich Koerner
tle4 wrote:
>
<snip>
> It does not tell you what silverface circuit. I would guess it would be an
> earlier one.
>
> Here are the titles to the 4 steps
>
> 1. Rewire bias supply and add two 220k resistors
> 2. Replace 4 resistors in phase inverter
> 3. Remove parasitic supression caps
> 4. Change 5u4 rectifier tube to 5ar4/gz34 and check bias
There is a lot more to it than these few steps.
And, the most important one omitted.
Regards,
Rich Koerner,
Time Electronics.
http://www.timeelect.com
Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers
Liberty Nym-Shifter
Guitar Player Magazine
Vol. 42 #7
Questions? guit...@musicplayer.com
PAGE 192, July 2008 Edn. [Al Deola on Cover]
Cool interviews w/ Steve Stevens and Steve Howe-
A whole Tele Licks section...
Wonderful Wes Montgomery section...
The ed. actively solicits coverage of *new* blood on pg. 9...
Me, I love all the old blood...unless Joe Bonamassa is included as
"new" ;-)
Separately, check out AMPLIFIERS: (21 of 'em! not including the
"Showdown" section) ---> http://guitarplayertv.com/
Silverface to Blackface Conversion Mod. Cautionary Statement:.
Amplifiers contain voltages high enough to Kill you even after the amp
has been powered Off ! ...
www.schematicheaven.com/mods/silver2blackmod.htm - 6k - Cached - Similar
pages - Note this
[PDF] Silverface to Blackface mod
File Format: PDF/Adobe Acrobat - View as HTML
Silverface amps all sound better when modded back to blackface specs in
my opinion. I will outline the mods below. However, ...
blueguitar.org/new/schem/fender/modnotes/mga-sf_bf_mod.pdf - Similar
pages - Note this
Silverface to Blackface mod
Silverface amps all sound better when modded back to blackface specs in
my opinion. I will outline the mods below. However, some of the changes
that Fender ...
acruhl.freeshell.org/mga/main/sf_bf_mod.html - 9k - Cached - Similar
pages - Note this
Tube Love: 05/01/2003 - 05/31/2003Silverface to Blackface Conversion Mod
The Mod: Starting in 1968, Fender began the move into the Silverface Era
under CBS owned Fender. ...
www.ultrajosh.com/tubeamp/2003_05_01_archive.html - 62k - Cached -
Similar pages - Note this
Newsletter
Silverface vs. Blackface. Apparently there is still a little confusion
about the .... up and asked me if I could use this amp to perform the
desired mod on. ...
www.griblinengineering.com/newsletter.htm - 26k - Cached - Similar pages
- Note this
Silverface Twin at last !! (Now with pics) [Archive] - Fender ...Aug 27,
2004 ... i have a mv silverface pro reverb and i love it too. super loud
super ... If you have a better set of speakers, then the blackface mod
will ...
www.myguitarplace.com/forum/archive/index.php/t-21625.html - 15k -
Cached - Similar pages - Note this
Mike Schway
Rich Koerner <ri...@timeelect.com> wrote:
> > It does not tell you what silverface circuit. I would guess it would be an
> > earlier one.
> >
> > Here are the titles to the 4 steps
> >
> > 1. Rewire bias supply and add two 220k resistors
> > 2. Replace 4 resistors in phase inverter
> > 3. Remove parasitic supression caps
> > 4. Change 5u4 rectifier tube to 5ar4/gz34 and check bias
>
> There is a lot more to it than these few steps.
>
> And, the most important one omitted.
OK, Rich WHICH is the most important one? ;-)
Candidates:
1) P/I input cap value
2) midrange tone stack cap value
3) bias supply filter (single 50uF instead of 2 stage 70uF)
3.5) Ditch that wonky semi-cathode biased scheme....only seen in the
AB568.
and
4) rip out all the wiring and do it RIGHT!
My vote goes to #1, 3 and 2 (in that order).
I'm guessing you're thinking #4 (!!!!!!!!!!!!!!!!) ;-)
--Mike
--------------------------------------------------------------------
Mike Schway | [Picture your favorite quote here]
msc...@nas.com |
--------------------------------------------------------------------
Ether
Mike Schway wrote:
> In article <4850C639...@timeelect.com>,
> Rich Koerner <ri...@timeelect.com> wrote:
>
> > > It does not tell you what silverface circuit. I would guess it would be an
> > > earlier one.
> > >
> > > Here are the titles to the 4 steps
> > >
> > > 1. Rewire bias supply and add two 220k resistors
> > > 2. Replace 4 resistors in phase inverter
> > > 3. Remove parasitic supression caps
> > > 4. Change 5u4 rectifier tube to 5ar4/gz34 and check bias
> >
> > There is a lot more to it than these few steps.
> >
> > And, the most important one omitted.
>
> OK, Rich WHICH is the most important one? ;-)
>
> Candidates:
> 1) P/I input cap value
Very important.
> 2) midrange tone stack cap value
Somewaht important.
> 3) bias supply filter (single 50uF instead of 2 stage 70uF)
Why would you want to do that? More filtering = less bias ripple.
> 3.5) Ditch that wonky semi-cathode biased scheme....only seen in the
> AB568.
Definitely.
> and
> 4) rip out all the wiring and do it RIGHT!
Well, yeah, if the lead dress is crap and is causing oscillations.
>
> My vote goes to #1, 3 and 2 (in that order).
1 & 2 -- forget 3.
>
> I'm guessing you're thinking #4 (!!!!!!!!!!!!!!!!) ;-)
>
> --Mike
Rich would. !!!!!!!!!!!!!!!!!!!!!!!!!!
--E
Mike Schway
<6f741a3f-9820-4ca6...@z66g2000hsc.googlegroups.com>,
Ether <et...@x-mail.net> wrote:
> > 3) bias supply filter (single 50uF instead of 2 stage 70uF)
>
> Why would you want to do that? More filtering = less bias ripple.
Sure, the more capacity in the bias supply the tighter and punchier the
amp will be; and in my experience the BF bias supply (one stage 50uF)
indeed makes for a looser sounding amp. But that's not necessarily a bad
thing for a guitar amp (bad for bass, but maybe not so bad for guitar).
A matter of personal taste, I suppose. At any rate, it's a worthwhile
experiment to try.
Rich Koerner
I'm going to have to work up a page on the Super Reverb for my web site down the road.
Not mentioning what SF version is at hand is a problem.
If you have the 70 watt SF Super Reverb.... boy do you have your work cut out for you.
However, setting up of those babies in the right fashion makes for a very KILLER Super Reverb.
<thinking>
For now, let me keep thing in a general context, for the sake of BF and early SF perspective, and
awareness.
From 1964 to 1969, in speakers alone, there are noticeable differences in the many different
speakers that Fender shipped in their Super Reverbs.
Of those, the alnico and the many ceramics, which is your base reference point for the targeted
standard?
Not all these speakers sounded the same. Personally, one of the ceramic swiss cheese framed 10's
were their best.
However, that is just a me thing.
There were also the transformer changes the went along the way in the time line too. Voltage
differences and current draw limits make for differences in a Super Reverb's performance too. These
little things make the differences when compared side by side.
Then, there are the other equally fine points that are most often glossed over as not being that
important for consideration in the SF to BF conversions.
What it all boils down to is, the exact voltages, on the exact tubes, so the exact speakers, with a
power supply response characteristic, with the properly referenced EQ within the different stages of
the Super Reverb. Or, any other amplifier where a similar goal if the point of the quest.
What is omitted from the four points of focus depends on much detail you want to get into. For most
these four points is all it takes. For others, close is not good enough.
If you are one of those cats, you have to have a clearly defined target. Then, the small details
become the things that you have to jump on.
First the exact tubes and speakers are a must.
The proper voltages from the power supply's divider string has to be addressed. Those rascals
changed in the time line. Depending on the transformers sitting in your SF, you either can use the
stock resistor string, or have to calculate new values to get all the voltages to each of the stages
to the proper targeted BF values.
Then, just looking into the time line changes to the reverb alone, is an important consideration
too. If the tank isn't driven right, the reverb isn't going to sound right. The big plate NOS 12AT7
is a nice thing to have in that socket to drive the reverb tank with a 2.2K kathode resistor.
On the way back, make sure all the caps are the right BF values too.
Depending on the type of by-pass and coupling caps that sit in the subject SF Super Reverb, few to
all may need replacing because of value changes.
Slap both bias adj and bal into the amp.
I like the AB763 PI ckt.
I'd use only the 5AR4. (I use SI diodes in mine)
Also,... GE, Sylvania, or RCA for tubes.
After this is done, the suppression caps are pulled, and lead dress is the final move.
If I gave this more thought, I may find some things to add I may have forgotten in the throw
together post.
Liberty Nym-Shifter
nm...@wt.net
>
> Specialists in Live Sound FOH Engineering,
> Music & Studio Production,
> Vintage Instruments, and Tube Amplifiers
Hummm. I've got one of the last 45 watters.. A 77..
It's been "blackfaced" but I really don't know what all they
did to it. It was done at some shop in Austin where I bought
it, but I forget to ask the guy who actually did it.
The work was done not long before I bought it.
It's worked and sounded fine, so I never have messed with
it, or even pulled the chassis yet..
"If it ain't broke, I ain't got time to mess with it"... :/
They did totally yank the master volume pot..
Myself, I would have left it in, even if unwired..
But, like I say, I didn't do it..
It was totally recapped, and I assume they went to
blackface values, but I've never looked yet.
Mine is using the S/S rectifier.. I've considered
going back to the tube, cuz I like an earlier
breakup and slightly lower power, but too lazy
to mess with it.
Mine uses the 4x10 Oxford? ceramics..
Many blues players don't care for em, but I've
heard some rockers that like em..
Mine sound fine to me, but I've never tried
the alnico's to compare..
Whatever they did, it's a good sounding amp.
I consider it my best amp really..
It's one mean blues machine..
And my other "decent" amp is a 74 Traynor Bassmaster
mk2.."100 watt version" It's no slouch, but no reverb,
etc..
It's my poor mans plexi clone... I need to get off my
butt and recap it.. All the caps are original, and
it's starting to get a bit funky..
Ether
You mean, adding a choke, disconnecting the UL taps, changing the PT,
etc., etc.? Not worth it. Unless you're willing to do the work for
free!
>
> <thinking>
>
> For now, let me keep thing in a general context, for the sake of BF and early SF perspective, and
> awareness.
>
> From 1964 to 1969, in speakers alone, there are noticeable differences in the many different
> speakers that Fender shipped in their Super Reverbs.
>
> Of those, the alnico and the many ceramics, which is your base reference point for the targeted
> standard?
>
> Not all these speakers sounded the same. Personally, one of the ceramic swiss cheese framed 10's
> were their best.
The alnicos are pretty good, too.
> However, that is just a me thing.
>
> There were also the transformer changes the went along the way in the time line too. Voltage
> differences and current draw limits make for differences in a Super Reverb's performance too. These
> little things make the differences when compared side by side.
The voltage differences between BF and SF are the bigger issue. The SF
PT's have higher secondary voltages, so if you try to put a 5AR4 or
diodes in a SFSR, the B+ voltage winds up being way too high, and the
amps sounds brittle. Not to mention that the other voltages in the amp
will be high, too. The differences in current supply from the BF and
SF PT's aren't that big a deal. Yeah, the 5AR4 sounds great in a
BFSR, but if you've got a SFSR, you're best off keeping the 5U4 in
there.
>
> Then, there are the other equally fine points that are most often glossed over as not being that
> important for consideration in the SF to BF conversions.
>
> What it all boils down to is, the exact voltages, on the exact tubes, so the exact speakers, with a
> power supply response characteristic, with the properly referenced EQ within the different stages of
> the Super Reverb. Or, any other amplifier where a similar goal if the point of the quest.
>
> What is omitted from the four points of focus depends on much detail you want to get into. For most
> these four points is all it takes. For others, close is not good enough.
>
> If you are one of those cats, you have to have a clearly defined target. Then, the small details
> become the things that you have to jump on.
>
> First the exact tubes and speakers are a must.
>
> The proper voltages from the power supply's divider string has to be addressed. Those rascals
> changed in the time line.
Yeah, but--That's usually not that big a deal, either--especially
compared to the controlling the plate and B+ voltage coming from the
rectifier. Often, you find SF amps with the old BF power ladder
resistor values anyway.
> Depending on the transformers sitting in your SF, you either can use the
> stock resistor string, or have to calculate new values to get all the voltages to each of the stages
> to the proper targeted BF values.
The SF preamp voltages produce some nice tones, too, so I wouldn't
worry about that right away as part of a BF conversion. The phase
inverter changes are often all you need for great sound.
> Then, just looking into the time line changes to the reverb alone, is an important consideration
> too. If the tank isn't driven right, the reverb isn't going to sound right. The big plate NOS 12AT7
> is a nice thing to have in that socket to drive the reverb tank with a 2.2K kathode resistor.
Yeah, good tubes often make a bigger difference than pretty much
anything else. Shitty tubes can make a BF amp sound like crap.
>
> On the way back, make sure all the caps are the right BF values too.
Especially the PI coupling cap. Though the higher .01uF SF coupling
cap sounds bigger, though it passes too much bass at higher volumes.
> Depending on the type of by-pass and coupling caps that sit in the subject SF Super Reverb, few to
> all may need replacing because of value changes.
Those things are far more durable than you would expect, even after
30-40 years.
> Slap both bias adj and bal into the amp.
If you don't mind fiddling with that. As long as you use closely
matched tubes, the bias adjust control is all you really need.
>
> I like the AB763 PI ckt.
Much preferred.
>
> I'd use only the 5AR4. (I use SI diodes in mine)
Not an option with most SF amps. The B+ voltage winds up being too
high.
> Also,... GE, Sylvania, or RCA for tubes.
Well, that goes without saying! Telefunken, Mullard, and Amperex will
do in a pinch.
>
> After this is done, the suppression caps are pulled, and lead dress is the final move.
Many of the SF amps--at least earlier ones--don't really need lead
dress adjustment, but it can't hurt. Some of the later 70s amps are a
mess.
>
> If I gave this more thought, I may find some things to add I may have forgotten in the throw
> together post.
You forgot about adding a dash of mojo. Doesn't sound the same without
it.
--E
Stephen Cowell
"Ether" <et...@x-mail.net> wrote
> Rich Koerner wrote:
...
>> After this is done, the suppression caps are pulled, and lead dress is
>> the final move.
>
> Many of the SF amps--at least earlier ones--don't really need lead
> dress adjustment, but it can't hurt. Some of the later 70s amps are a
> mess.
Any SF with stranded wiring will need re-wiring... unless
you want to leave the supressor caps in. You can't do
lead dress with wire that won't stay where you put it.
This *is* the hard-to-define 'mojo' part... magic.
Throw in a John The Conqueror root and a black
cat bone...
__
Steve
.
Rich Koerner
Ether wrote:
<SNIP>
> > I'm going to have to work up a page on the Super Reverb for my web site down the road.
> >
> > Not mentioning what SF version is at hand is a problem.
> >
> > If you have the 70 watt SF Super Reverb.... boy do you have your work cut out for you.
> >
> > However, setting up of those babies in the right fashion makes for a very KILLER Super Reverb.
>
> You mean, adding a choke, disconnecting the UL taps, changing the PT,
> etc., etc.?
Correct.
> Not worth it. Unless you're willing to do the work for
> free!
You'll change your mind once you experienced it.
>
> >
> > <thinking>
> >
> > For now, let me keep thing in a general context, for the sake of BF and early SF perspective, and
> > awareness.
> >
> > From 1964 to 1969, in speakers alone, there are noticeable differences in the many different
> > speakers that Fender shipped in their Super Reverbs.
> >
> > Of those, the alnico and the many ceramics, which is your base reference point for the targeted
> > standard?
> >
> > Not all these speakers sounded the same. Personally, one of the ceramic swiss cheese framed 10's
> > were their best.
>
> The alnicos are pretty good, too.
>
> > However, that is just a me thing.
> >
> > There were also the transformer changes the went along the way in the time line too. Voltage
> > differences and current draw limits make for differences in a Super Reverb's performance too. These
> > little things make the differences when compared side by side.
>
> The voltage differences between BF and SF are the bigger issue. The SF
> PT's have higher secondary voltages, so if you try to put a 5AR4 or
> diodes in a SFSR, the B+ voltage winds up being way too high, and the
> amps sounds brittle.
High voltage on tubes run too cold causes what I believe you are talking about.
Bias by numbers guys always have that problem.
> Not to mention that the other voltages in the amp
> will be high, too.
Which, is not a problem to correct.
> The differences in current supply from the BF and
> SF PT's aren't that big a deal. Yeah, the 5AR4 sounds great in a
> BFSR, but if you've got a SFSR, you're best off keeping the 5U4 in
> there.
Not an always absolute.
Which, depends on the exact targeted Super Reverb results of the owner/user.
> > Then, there are the other equally fine points that are most often glossed over as not being that
> > important for consideration in the SF to BF conversions.
> >
> > What it all boils down to is, the exact voltages, on the exact tubes, so the exact speakers, with a
> > power supply response characteristic, with the properly referenced EQ within the different stages of
> > the Super Reverb. Or, any other amplifier where a similar goal if the point of the quest.
> >
> > What is omitted from the four points of focus depends on much detail you want to get into. For most
> > these four points is all it takes. For others, close is not good enough.
> >
> > If you are one of those cats, you have to have a clearly defined target. Then, the small details
> > become the things that you have to jump on.
> >
> > First the exact tubes and speakers are a must.
> >
> > The proper voltages from the power supply's divider string has to be addressed. Those rascals
> > changed in the time line.
>
> Yeah, but--That's usually not that big a deal, either--especially
> compared to the controlling the plate and B+ voltage coming from the
> rectifier. Often, you find SF amps with the old BF power ladder
> resistor values anyway.
Yet, this is not addressed by many as an important point of focus. But it is if you want to have
the Super Reverb that makes the difference in performance other don't achieve.
> > Depending on the transformers sitting in your SF, you either can use the
> > stock resistor string, or have to calculate new values to get all the voltages to each of the stages
> > to the proper targeted BF values.
>
> The SF preamp voltages produce some nice tones, too, so I wouldn't
> worry about that right away as part of a BF conversion. The phase
> inverter changes are often all you need for great sound.
>
> > Then, just looking into the time line changes to the reverb alone, is an important consideration
> > too. If the tank isn't driven right, the reverb isn't going to sound right. The big plate NOS 12AT7
> > is a nice thing to have in that socket to drive the reverb tank with a 2.2K kathode resistor.
>
> Yeah, good tubes often make a bigger difference than pretty much
> anything else. Shitty tubes can make a BF amp sound like crap.
>
> >
> > On the way back, make sure all the caps are the right BF values too.
>
> Especially the PI coupling cap. Though the higher .01uF SF coupling
> cap sounds bigger, though it passes too much bass at higher volumes.
Turn down the bass control. That's what they are there for.
> > Depending on the type of by-pass and coupling caps that sit in the subject SF Super Reverb, few to
> > all may need replacing because of value changes.
>
> Those things are far more durable than you would expect, even after
> 30-40 years.
I don't care how old they are. I measure 'em all. If they are off value, they are out of the amp.
> > Slap both bias adj and bal into the amp.
>
> If you don't mind fiddling with that. As long as you use closely
> matched tubes, the bias adjust control is all you really need.
Not if you want to feed the amp Polished Turds.
> > I like the AB763 PI ckt.
>
> Much preferred.
>
> >
> > I'd use only the 5AR4. (I use SI diodes in mine)
>
> Not an option with most SF amps. The B+ voltage winds up being too
> high.
Too high? Well, I guess I never saw it as a problem of any kind.
> > Also,... GE, Sylvania, or RCA for tubes.
>
> Well, that goes without saying! Telefunken, Mullard, and Amperex will
> do in a pinch.
>
> >
> > After this is done, the suppression caps are pulled, and lead dress is the final move.
>
> Many of the SF amps--at least earlier ones--don't really need lead
> dress adjustment, but it can't hurt. Some of the later 70s amps are a
> mess.
>
> >
> > If I gave this more thought, I may find some things to add I may have forgotten in the throw
> > together post.
>
> You forgot about adding a dash of mojo. Doesn't sound the same without
> it.
Actually, I rip out the boost ckt, and leave the master volume ckt in most of the Super Reverbs that
leave the shop.
JP
<sco...@sbcglobal.net> wrote:
>John The Conqueror root
You need to eat a mess of these SC. Will likely fix what ails ya...
Ether
Stephen Cowell wrote:
> "Ether" <et...@x-mail.net> wrote
> > Rich Koerner wrote:
>
> ...
>
> >> After this is done, the suppression caps are pulled, and lead dress is
> >> the final move.
> >
> > Many of the SF amps--at least earlier ones--don't really need lead
> > dress adjustment, but it can't hurt. Some of the later 70s amps are a
> > mess.
>
> Any SF with stranded wiring will need re-wiring... unless
> you want to leave the supressor caps in. You can't do
> lead dress with wire that won't stay where you put it.
Many of the SF amps--at least earlier ones--don't really need lead
dress adjustment, but it can't hurt. Some of the later 70s amps are a
mess.
It doesn't matter what kind of wire was used if it's already in the
right place. If the
wire is in the right place, you don't need the suppressor caps.
> This *is* the hard-to-define 'mojo' part... magic.
> Throw in a John The Conqueror root and a black
> cat bone...
Not really. Physics is physics. Either the circuit oscillates
uncontrollably, or it doesn't.
--E
Ether
> On Tue, 17 Jun 2008 12:58:22 -0400, Rich Koerner wrote:
> >> Not an option with most SF amps. The B+ voltage winds up being too high.
>
> > Too high? Well, I guess I never saw it as a problem of any kind.
>
> after recapping the HV. It didn't pose much of a problem at all.
That's way too high. It might work fine--with the right output tubes
and filter caps--but
540 volts on the 6L6GC plates will make for a hard, sterile tone.
--E
Ether
Rich Koerner wrote:
> Ether wrote:
>
> <SNIP>
>
>
> > > I'm going to have to work up a page on the Super Reverb for my web site down the road.
> > >
> > > Not mentioning what SF version is at hand is a problem.
> > >
> > > If you have the 70 watt SF Super Reverb.... boy do you have your work cut out for you.
> > >
> > > However, setting up of those babies in the right fashion makes for a very KILLER Super Reverb.
> >
> > You mean, adding a choke, disconnecting the UL taps, changing the PT,
> > etc., etc.?
>
> Correct.
>
> > Not worth it. Unless you're willing to do the work for
> > free!
>
> You'll change your mind once you experienced it.
You'd be better off putting the money into an amp that designed the
way you want--and saving the effort.
> > >
> > > <thinking>
> > >
> > > For now, let me keep thing in a general context, for the sake of BF and early SF perspective, and
> > > awareness.
> > >
> > > From 1964 to 1969, in speakers alone, there are noticeable differences in the many different
> > > speakers that Fender shipped in their Super Reverbs.
> > >
> > > Of those, the alnico and the many ceramics, which is your base reference point for the targeted
> > > standard?
> > >
> > > Not all these speakers sounded the same. Personally, one of the ceramic swiss cheese framed 10's
> > > were their best.
> >
> > The alnicos are pretty good, too.
> >
> > > However, that is just a me thing.
> > >
> > > There were also the transformer changes the went along the way in the time line too. Voltage
> > > differences and current draw limits make for differences in a Super Reverb's performance too. These
> > > little things make the differences when compared side by side.
> >
> > The voltage differences between BF and SF are the bigger issue. The SF
> > PT's have higher secondary voltages, so if you try to put a 5AR4 or
> > diodes in a SFSR, the B+ voltage winds up being way too high, and the
> > amps sounds brittle.
>
> High voltage on tubes run too cold causes what I believe you are talking about.
High voltage--period--is the problem, regardless of bias. Did you read
Jim's comments on the JCM vs. JMP 800? The amp with the lower plate
voltage will have the sweeter tone.
> Bias by numbers guys always have that problem.
I always trust my ears.
>
> > Not to mention that the other voltages in the amp
> > will be high, too.
>
> Which, is not a problem to correct.
Just an unnecessary pain in the ass. And if the plate voltage is too
high, it doesn't matter much what's going on in the preamp stages. The
tone is going to suck regardless.
>
> > The differences in current supply from the BF and
> > SF PT's aren't that big a deal. Yeah, the 5AR4 sounds great in a
> > BFSR, but if you've got a SFSR, you're best off keeping the 5U4 in
> > there.
>
>
> Not an always absolute.
Pretty much!
> Which, depends on the exact targeted Super Reverb results of the owner/user.
Unless the owner likes the hard and sterile tone caused by the high
plate voltage, you're out of luck.
>
> > > Then, there are the other equally fine points that are most often glossed over as not being that
> > > important for consideration in the SF to BF conversions.
> > >
> > > What it all boils down to is, the exact voltages, on the exact tubes, so the exact speakers, with a
> > > power supply response characteristic, with the properly referenced EQ within the different stages of
> > > the Super Reverb. Or, any other amplifier where a similar goal if the point of the quest.
> > >
> > > What is omitted from the four points of focus depends on much detail you want to get into. For most
> > > these four points is all it takes. For others, close is not good enough.
> > >
> > > If you are one of those cats, you have to have a clearly defined target. Then, the small details
> > > become the things that you have to jump on.
> > >
> > > First the exact tubes and speakers are a must.
> > >
> > > The proper voltages from the power supply's divider string has to be addressed. Those rascals
> > > changed in the time line.
> >
> > Yeah, but--That's usually not that big a deal, either--especially
> > compared to the controlling the plate and B+ voltage coming from the
> > rectifier. Often, you find SF amps with the old BF power ladder
> > resistor values anyway.
>
> Yet, this is not addressed by many as an important point of focus. But it is if you want to have
> the Super Reverb that makes the difference in performance other don't achieve.
All else being equal, yes. But like I said, if the output tube plate
voltage is too high, tweaking the preamp voltages is pointless.
>
> > > Depending on the transformers sitting in your SF, you either can use the
> > > stock resistor string, or have to calculate new values to get all the voltages to each of the stages
> > > to the proper targeted BF values.
> >
> > The SF preamp voltages produce some nice tones, too, so I wouldn't
> > worry about that right away as part of a BF conversion. The phase
> > inverter changes are often all you need for great sound.
> >
> > > Then, just looking into the time line changes to the reverb alone, is an important consideration
> > > too. If the tank isn't driven right, the reverb isn't going to sound right. The big plate NOS 12AT7
> > > is a nice thing to have in that socket to drive the reverb tank with a 2.2K kathode resistor.
> >
> > Yeah, good tubes often make a bigger difference than pretty much
> > anything else. Shitty tubes can make a BF amp sound like crap.
> >
> > >
> > > On the way back, make sure all the caps are the right BF values too.
> >
> > Especially the PI coupling cap. Though the higher .01uF SF coupling
> > cap sounds bigger, though it passes too much bass at higher volumes.
>
> Turn down the bass control. That's what they are there for.
Not the same thing. You can't achieve the same tonal characteristics
when the PI coupling cap value is off by a factor of ten. Play a BFSR
and SFSR side by side--you'll see what I mean.
>
> > > Depending on the type of by-pass and coupling caps that sit in the subject SF Super Reverb, few to
> > > all may need replacing because of value changes.
> >
> > Those things are far more durable than you would expect, even after
> > 30-40 years.
>
> I don't care how old they are. I measure 'em all. If they are off value, they are out of the amp.
If they're out of spec--sure. But that's rarer than you'd think--even
on a decades-old amp.
>
> > > Slap both bias adj and bal into the amp.
> >
> > If you don't mind fiddling with that. As long as you use closely
> > matched tubes, the bias adjust control is all you really need.
>
> Not if you want to feed the amp Polished Turds.
A lot of new tubes suck. But a lot of new tubes can also be bought
closely matched--and stay that way. No great need for a balance
control.
>
> > > I like the AB763 PI ckt.
> >
> > Much preferred.
> >
> > >
> > > I'd use only the 5AR4. (I use SI diodes in mine)
> >
> > Not an option with most SF amps. The B+ voltage winds up being too
> > high.
>
> Too high? Well, I guess I never saw it as a problem of any kind.
Not if you like hard, sterile tone. I guess some people ain't that
particular!
>
> > > Also,... GE, Sylvania, or RCA for tubes.
> >
> > Well, that goes without saying! Telefunken, Mullard, and Amperex will
> > do in a pinch.
> >
> > >
> > > After this is done, the suppression caps are pulled, and lead dress is the final move.
> >
> > Many of the SF amps--at least earlier ones--don't really need lead
> > dress adjustment, but it can't hurt. Some of the later 70s amps are a
> > mess.
> >
> > >
> > > If I gave this more thought, I may find some things to add I may have forgotten in the throw
> > > together post.
> >
> > You forgot about adding a dash of mojo. Doesn't sound the same without
> > it.
>
> Actually, I rip out the boost ckt, and leave the master volume ckt in most of the Super Reverbs that
> leave the shop.
Not a big deal. Having an MV pot in there is much less of an evil than
having B+ that's 100V too high.
--E
Stephen Cowell
"Ether" <et...@x-mail.net> wrote
> Stephen Cowell wrote:
...
>> Any SF with stranded wiring will need re-wiring... unless
>> you want to leave the supressor caps in. You can't do
>> lead dress with wire that won't stay where you put it.
>
> Many of the SF amps--at least earlier ones--don't really need lead
> dress adjustment, but it can't hurt. Some of the later 70s amps are a
> mess.
Early SF had solid wire... my '68 Twin does, FI. Yanking
the suppressors is a crapshoot, especially with stranded wire
moving around in there.
> It doesn't matter what kind of wire was used if it's already in the
> right place. If the
> wire is in the right place, you don't need the suppressor caps.
The point is, solid wire stays where you put it. Stranded
doesn't... unless you go to *great* lengths to tie it back,
etc. Much easier to just rewire the thing in solid... looks
cooler too.
>> This *is* the hard-to-define 'mojo' part... magic.
>> Throw in a John The Conqueror root and a black
>> cat bone...
>
> Not really. Physics is physics. Either the circuit oscillates
> uncontrollably, or it doesn't.
... or it oscillates only on voltage peaks. There's a whole
continuum of parasitic effect, from not at all to RF CW
transmitter.
__
Steve
.
Rich Koerner
Ether wrote:
>
> Rich Koerner wrote:
> > Ether wrote:
> >
> > <SNIP>
> >
> >
> > > > I'm going to have to work up a page on the Super Reverb for my web site down the road.
> > > >
> > > > Not mentioning what SF version is at hand is a problem.
> > > >
> > > > If you have the 70 watt SF Super Reverb.... boy do you have your work cut out for you.
> > > >
> > > > However, setting up of those babies in the right fashion makes for a very KILLER Super Reverb.
> > >
> > > You mean, adding a choke, disconnecting the UL taps, changing the PT,
> > > etc., etc.?
> >
> > Correct.
> >
> > > Not worth it. Unless you're willing to do the work for
> > > free!
> >
> > You'll change your mind once you experienced it.
>
> You'd be better off putting the money into an amp that designed the
> way you want--and saving the effort.
How would the uneducated musician in amplifier design, have basis to make an informed decision on
such?
You are expert on amp design?
>
> > > >
> > > > <thinking>
> > > >
> > > > For now, let me keep thing in a general context, for the sake of BF and early SF perspective, and
> > > > awareness.
> > > >
> > > > From 1964 to 1969, in speakers alone, there are noticeable differences in the many different
> > > > speakers that Fender shipped in their Super Reverbs.
> > > >
> > > > Of those, the alnico and the many ceramics, which is your base reference point for the targeted
> > > > standard?
> > > >
> > > > Not all these speakers sounded the same. Personally, one of the ceramic swiss cheese framed 10's
> > > > were their best.
> > >
> > > The alnicos are pretty good, too.
> > >
> > > > However, that is just a me thing.
> > > >
> > > > There were also the transformer changes the went along the way in the time line too. Voltage
> > > > differences and current draw limits make for differences in a Super Reverb's performance too. These
> > > > little things make the differences when compared side by side.
> > >
> > > The voltage differences between BF and SF are the bigger issue. The SF
> > > PT's have higher secondary voltages, so if you try to put a 5AR4 or
> > > diodes in a SFSR, the B+ voltage winds up being way too high, and the
> > > amps sounds brittle.
> >
> > High voltage on tubes run too cold causes what I believe you are talking about.
>
> High voltage--period--is the problem, regardless of bias.
Where the hell did this notion that high voltage is any kind of problem associated with poor
performance.
Think in terms of a high order of performance magnitude, and the error in this thinking can be
found.
> Did you read
> Jim's comments on the JCM vs. JMP 800? The amp with the lower plate
> voltage will have the sweeter tone.
Well, any time you want to achieve low performance from a high performance design, you can arrive at
such a conclusion because of the error in thinking behind the exercise.
> > Bias by numbers guys always have that problem.
>
> I always trust my ears.
But, this leads to the present conclusions in error.
>
> >
> > > Not to mention that the other voltages in the amp
> > > will be high, too.
> >
> > Which, is not a problem to correct.
>
> Just an unnecessary pain in the ass. And if the plate voltage is too
> high, it doesn't matter much what's going on in the preamp stages. The
> tone is going to suck regardless.
WRONG!
> >
> > > The differences in current supply from the BF and
> > > SF PT's aren't that big a deal. Yeah, the 5AR4 sounds great in a
> > > BFSR, but if you've got a SFSR, you're best off keeping the 5U4 in
> > > there.
> >
> >
> > Not an always absolute.
>
> Pretty much!
>
> > Which, depends on the exact targeted Super Reverb results of the owner/user.
>
> Unless the owner likes the hard and sterile tone caused by the high
> plate voltage, you're out of luck.
Again, a conclusion in error.
Here are the specs common to those tubes used in amp design.
http://www.timeelect.com/6550ap1.gif
http://www.timeelect.com/6550ap2.gif
http://www.timeelect.com/6550ap3.gif
http://www.timeelect.com/6550ap4.gif
http://www.timeelect.com/6550ap5.gif
http://www.timeelect.com/6550ap6.gif
http://www.timeelect.com/6550ap7.gif
http://www.timeelect.com/6550ap8.gif
This tube data represents what the vacuum actually does.
Point out the *tone suck points* you are talking about on the operating curves supplied, and I'll
show you a tube/s performing at improper operating points.
High voltage is NOT the cause for bad tone.
Improper tube operation and/or application IS.
> > > > Then, there are the other equally fine points that are most often glossed over as not being that
> > > > important for consideration in the SF to BF conversions.
> > > >
> > > > What it all boils down to is, the exact voltages, on the exact tubes, so the exact speakers, with a
> > > > power supply response characteristic, with the properly referenced EQ within the different stages of
> > > > the Super Reverb. Or, any other amplifier where a similar goal if the point of the quest.
> > > >
> > > > What is omitted from the four points of focus depends on much detail you want to get into. For most
> > > > these four points is all it takes. For others, close is not good enough.
> > > >
> > > > If you are one of those cats, you have to have a clearly defined target. Then, the small details
> > > > become the things that you have to jump on.
> > > >
> > > > First the exact tubes and speakers are a must.
> > > >
> > > > The proper voltages from the power supply's divider string has to be addressed. Those rascals
> > > > changed in the time line.
> > >
> > > Yeah, but--That's usually not that big a deal, either--especially
> > > compared to the controlling the plate and B+ voltage coming from the
> > > rectifier. Often, you find SF amps with the old BF power ladder
> > > resistor values anyway.
> >
> > Yet, this is not addressed by many as an important point of focus. But it is if you want to have
> > the Super Reverb that makes the difference in performance other don't achieve.
>
> All else being equal, yes. But like I said, if the output tube plate
> voltage is too high, tweaking the preamp voltages is pointless.
You really lack the understanding on how the vacuum tube really works.
> > > > Depending on the transformers sitting in your SF, you either can use the
> > > > stock resistor string, or have to calculate new values to get all the voltages to each of the stages
> > > > to the proper targeted BF values.
> > >
> > > The SF preamp voltages produce some nice tones, too, so I wouldn't
> > > worry about that right away as part of a BF conversion. The phase
> > > inverter changes are often all you need for great sound.
> > >
> > > > Then, just looking into the time line changes to the reverb alone, is an important consideration
> > > > too. If the tank isn't driven right, the reverb isn't going to sound right. The big plate NOS 12AT7
> > > > is a nice thing to have in that socket to drive the reverb tank with a 2.2K kathode resistor.
> > >
> > > Yeah, good tubes often make a bigger difference than pretty much
> > > anything else. Shitty tubes can make a BF amp sound like crap.
> > >
> > > >
> > > > On the way back, make sure all the caps are the right BF values too.
> > >
> > > Especially the PI coupling cap. Though the higher .01uF SF coupling
> > > cap sounds bigger, though it passes too much bass at higher volumes.
> >
> > Turn down the bass control. That's what they are there for.
>
> Not the same thing. You can't achieve the same tonal characteristics
> when the PI coupling cap value is off by a factor of ten. Play a BFSR
> and SFSR side by side--you'll see what I mean.
In the example of too much bass, the type of filter (fixed or variable), or where it's located,
still performs the same function.
> > > > Depending on the type of by-pass and coupling caps that sit in the subject SF Super Reverb, few to
> > > > all may need replacing because of value changes.
> > >
> > > Those things are far more durable than you would expect, even after
> > > 30-40 years.
> >
> > I don't care how old they are. I measure 'em all. If they are off value, they are out of the amp.
>
> If they're out of spec--sure. But that's rarer than you'd think--even
> on a decades-old amp.
Not by my experience.
How many kathode caps have you measured from the amps of long ago still on spec?
http://www.timeelect.com/eh-150.htm
http://www.timeelect.com/vinfpa.htm
http://www.timeelect.com/vinchamp.htm
http://www.timeelect.com/concert.htm
Coupling caps too.
ALL of the caps from the old days age and drift.
Like I said. I measure 'em all. If they are off value, they are out of the amp.
Depending on the type of cap, the value, type of circuit they are in.... temperature is also a
factor in drift.
Did you know that?
> > > > Slap both bias adj and bal into the amp.
> > >
> > > If you don't mind fiddling with that. As long as you use closely
> > > matched tubes, the bias adjust control is all you really need.
> >
> > Not if you want to feed the amp Polished Turds.
>
> A lot of new tubes suck. But a lot of new tubes can also be bought
> closely matched--and stay that way. No great need for a balance
> control.
Well, if what you are saying is absolutely true... why have an adjustable bias control at all.
These tubes today that you say are manufactured so perfectly to stay MATCHED... they should all
therefore have equally a matched starting points in their life time too. RIGHT?
So, there is no need for ANY bias adjustments or re-adjustments EVER!
But then, there is the common mistaking notion that, it is the bias supply itself, that is the REAL
cause of any tube drifting problem in the equation.
> > > > I like the AB763 PI ckt.
> > >
> > > Much preferred.
> > >
> > > >
> > > > I'd use only the 5AR4. (I use SI diodes in mine)
> > >
> > > Not an option with most SF amps. The B+ voltage winds up being too
> > > high.
> >
> > Too high? Well, I guess I never saw it as a problem of any kind.
>
> Not if you like hard, sterile tone. I guess some people ain't that
> particular!
There is nothing sterile of hard sounding about an Ampeg VT-40.
Yet, there is 600 volts on the plates of the two 7027 tubes in that amp.
Didn't know that, did ya.
Then, there is nothing hard and sterile about a well set-up 1971 Super Lead with 535 volts B+
sitting on the plates of some nice Mullard EL-34's running on the warm side.
But, what you are going to object to is the FACT that, this amp is a HIGH PERFORMANCE *STAGE* AMP
and is over kill for your common bedroom, garage, and small club venues.
Using this 1971 Marshall JMP at the LOWER desired volume levels, you are naturally going to conclude
in error that, this great sounding HIGH PERFORMANCE *STAGE* AMP is now hard and sterile sounding
because of it's high voltage.
It's kind a like using a top fuel dragster to go food shopping and complaining about snapping your
neck every time you touch the gas pedal, having concluded that too much nitro entering the engine is
the problem.
> > > > Also,... GE, Sylvania, or RCA for tubes.
> > >
> > > Well, that goes without saying! Telefunken, Mullard, and Amperex will
> > > do in a pinch.
> > >
> > > >
> > > > After this is done, the suppression caps are pulled, and lead dress is the final move.
> > >
> > > Many of the SF amps--at least earlier ones--don't really need lead
> > > dress adjustment, but it can't hurt. Some of the later 70s amps are a
> > > mess.
> > >
> > > >
> > > > If I gave this more thought, I may find some things to add I may have forgotten in the throw
> > > > together post.
> > >
> > > You forgot about adding a dash of mojo. Doesn't sound the same without
> > > it.
> >
> > Actually, I rip out the boost ckt, and leave the master volume ckt in most of the Super Reverbs that
> > leave the shop.
>
> Not a big deal. Having an MV pot in there is much less of an evil than
> having B+ that's 100V too high.
>
> --E
Ether
Rich Koerner wrote:
> Ether wrote:
> >
> > Rich Koerner wrote:
> > > Ether wrote:
> > >
> > > <SNIP>
> > >
> > >
> > > > > I'm going to have to work up a page on the Super Reverb for my web site down the road.
> > > > >
> > > > > Not mentioning what SF version is at hand is a problem.
> > > > >
> > > > > If you have the 70 watt SF Super Reverb.... boy do you have your work cut out for you.
> > > > >
> > > > > However, setting up of those babies in the right fashion makes for a very KILLER Super Reverb.
> > > >
> > > > You mean, adding a choke, disconnecting the UL taps, changing the PT,
> > > > etc., etc.?
> > >
> > > Correct.
> > >
> > > > Not worth it. Unless you're willing to do the work for
> > > > free!
> > >
> > > You'll change your mind once you experienced it.
> >
> > You'd be better off putting the money into an amp that designed the
> > way you want--and saving the effort.
>
> How would the uneducated musician in amplifier design, have basis to make an informed decision on
> such?
By listening to the tone of various amps and making an informed
decision. Simple.
You proposed taking an ultralinear SR and converting it into a pseudo-
blackface. Why would you want to do that?--to achieve something closer
to blackface tone. Right? But with a UL Fender, there's only so close
you can get without replacing the PT. If blackface tone is what you
want, you're much better off starting with an earlier SF non-UL Fender
amp. It will require less labor and less $$.
> You are expert on amp design?
In this regard, yes.
> >
> > > > >
> > > > > <thinking>
> > > > >
> > > > > For now, let me keep thing in a general context, for the sake of BF and early SF perspective, and
> > > > > awareness.
> > > > >
> > > > > From 1964 to 1969, in speakers alone, there are noticeable differences in the many different
> > > > > speakers that Fender shipped in their Super Reverbs.
> > > > >
> > > > > Of those, the alnico and the many ceramics, which is your base reference point for the targeted
> > > > > standard?
> > > > >
> > > > > Not all these speakers sounded the same. Personally, one of the ceramic swiss cheese framed 10's
> > > > > were their best.
> > > >
> > > > The alnicos are pretty good, too.
> > > >
> > > > > However, that is just a me thing.
> > > > >
> > > > > There were also the transformer changes the went along the way in the time line too. Voltage
> > > > > differences and current draw limits make for differences in a Super Reverb's performance too. These
> > > > > little things make the differences when compared side by side.
> > > >
> > > > The voltage differences between BF and SF are the bigger issue. The SF
> > > > PT's have higher secondary voltages, so if you try to put a 5AR4 or
> > > > diodes in a SFSR, the B+ voltage winds up being way too high, and the
> > > > amps sounds brittle.
> > >
> > > High voltage on tubes run too cold causes what I believe you are talking about.
> >
> > High voltage--period--is the problem, regardless of bias.
>
> Where the hell did this notion that high voltage is any kind of problem associated with poor
> performance.
Simple--tone.
> Think in terms of a high order of performance magnitude, and the error in this thinking can be
> found.
No error. A bunch of guys right here have agreed with the opinion
that higher plate voltage=degraded tone, in a Marshall JMP and in
various Fenders. I am not alone.
>
> > Did you read
> > Jim's comments on the JCM vs. JMP 800? The amp with the lower plate
> > voltage will have the sweeter tone.
>
> Well, any time you want to achieve low performance from a high performance design, you can arrive at
> such a conclusion because of the error in thinking behind the exercise.
No error. The ears don't lie. Well, mine, anyway. Your ears may vary,
apparently.
>
> > > Bias by numbers guys always have that problem.
> >
> > I always trust my ears.
>
> But, this leads to the present conclusions in error.
No error, Rich, The ears don't lie.
>
> >
> > >
> > > > Not to mention that the other voltages in the amp
> > > > will be high, too.
> > >
> > > Which, is not a problem to correct.
> >
> > Just an unnecessary pain in the ass. And if the plate voltage is too
> > high, it doesn't matter much what's going on in the preamp stages. The
> > tone is going to suck regardless.
>
> WRONG!
Like I said, many others agree with me. You may like, hard, brittle
tone in your Fenders. Not me.
>
> > >
> > > > The differences in current supply from the BF and
> > > > SF PT's aren't that big a deal. Yeah, the 5AR4 sounds great in a
> > > > BFSR, but if you've got a SFSR, you're best off keeping the 5U4 in
> > > > there.
> > >
> > >
> > > Not an always absolute.
> >
> > Pretty much!
> >
> > > Which, depends on the exact targeted Super Reverb results of the owner/user.
> >
> > Unless the owner likes the hard and sterile tone caused by the high
> > plate voltage, you're out of luck.
>
> Again, a conclusion in error.
No error, Rich. The ears don't lie.
Give a listen to several Fender amps from 1964-1978 or so. As the
years wore on, Fender kept increasing the PT voltage--and plate
voltage--to increase wattage and clean headroom. And as the years wore
on and the plate voltage increased, the tone got worse. That's a major
reason why blackface amps are in such demand. Yes, there are other
design issues that we've covered--PI coupling cap value, etc.--but in
many of the Fender amps, the output tube plate voltage has the biggest
effect on tone.
>
> Here are the specs common to those tubes used in amp design.
>
> http://www.timeelect.com/6550ap1.gif
> http://www.timeelect.com/6550ap2.gif
> http://www.timeelect.com/6550ap3.gif
> http://www.timeelect.com/6550ap4.gif
> http://www.timeelect.com/6550ap5.gif
> http://www.timeelect.com/6550ap6.gif
> http://www.timeelect.com/6550ap7.gif
> http://www.timeelect.com/6550ap8.gif
>
>
> This tube data represents what the vacuum actually does.
Why are you posting links to 6550's when we're discussing a SF SR,
which uses 6L6GC output tubes? Sure, if you want to change the design
and equipment, you can get all kinds of different results. Don't move
the goalpaosts on us, Rich!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> Point out the *tone suck points* you are talking about on the operating curves supplied, and I'll
> show you a tube/s performing at improper operating points.
Ignore your 6550 curves, Rich, and lets get back to the 6L6GC. As you
yourself have said, every tube has its "sweet spot". For 6L6GC's in a
Fender circuit, that sweet spot is well south of 500 volts, and
probably closer to 450V. As you get near 500V and beyond, the tone
gets hard and brittle. That's why those Fender-like Music Man amps
with the high plate voltages sounded like crap.
> High voltage is NOT the cause for bad tone.
In a SF SR, it sure as hell is.
> Improper tube operation and/or application IS.
Right--like running a 6L6 at over 500V in a Fender circuit.
>
> > > > > Then, there are the other equally fine points that are most often glossed over as not being that
> > > > > important for consideration in the SF to BF conversions.
> > > > >
> > > > > What it all boils down to is, the exact voltages, on the exact tubes, so the exact speakers, with a
> > > > > power supply response characteristic, with the properly referenced EQ within the different stages of
> > > > > the Super Reverb. Or, any other amplifier where a similar goal if the point of the quest.
> > > > >
> > > > > What is omitted from the four points of focus depends on much detail you want to get into. For most
> > > > > these four points is all it takes. For others, close is not good enough.
> > > > >
> > > > > If you are one of those cats, you have to have a clearly defined target. Then, the small details
> > > > > become the things that you have to jump on.
> > > > >
> > > > > First the exact tubes and speakers are a must.
> > > > >
> > > > > The proper voltages from the power supply's divider string has to be addressed. Those rascals
> > > > > changed in the time line.
> > > >
> > > > Yeah, but--That's usually not that big a deal, either--especially
> > > > compared to the controlling the plate and B+ voltage coming from the
> > > > rectifier. Often, you find SF amps with the old BF power ladder
> > > > resistor values anyway.
> > >
> > > Yet, this is not addressed by many as an important point of focus. But it is if you want to have
> > > the Super Reverb that makes the difference in performance other don't achieve.
> >
> > All else being equal, yes. But like I said, if the output tube plate
> > voltage is too high, tweaking the preamp voltages is pointless.
>
> You really lack the understanding on how the vacuum tube really works.
I could just as easily say that you lack an ear for tone. And I would
be more likely to be right.
>
> > > > > Depending on the transformers sitting in your SF, you either can use the
> > > > > stock resistor string, or have to calculate new values to get all the voltages to each of the stages
> > > > > to the proper targeted BF values.
> > > >
> > > > The SF preamp voltages produce some nice tones, too, so I wouldn't
> > > > worry about that right away as part of a BF conversion. The phase
> > > > inverter changes are often all you need for great sound.
> > > >
> > > > > Then, just looking into the time line changes to the reverb alone, is an important consideration
> > > > > too. If the tank isn't driven right, the reverb isn't going to sound right. The big plate NOS 12AT7
> > > > > is a nice thing to have in that socket to drive the reverb tank with a 2.2K kathode resistor.
> > > >
> > > > Yeah, good tubes often make a bigger difference than pretty much
> > > > anything else. Shitty tubes can make a BF amp sound like crap.
> > > >
> > > > >
> > > > > On the way back, make sure all the caps are the right BF values too.
> > > >
> > > > Especially the PI coupling cap. Though the higher .01uF SF coupling
> > > > cap sounds bigger, though it passes too much bass at higher volumes.
> > >
> > > Turn down the bass control. That's what they are there for.
> >
> > Not the same thing. You can't achieve the same tonal characteristics
> > when the PI coupling cap value is off by a factor of ten. Play a BFSR
> > and SFSR side by side--you'll see what I mean.
>
> In the example of too much bass, the type of filter (fixed or variable), or where it's located,
> still performs the same function.
A bass filter in a different location in a circuit will often have a
dramatically different effect on the tone and behavior of an amp.
That's one of the many reasons that a BF SR doesn't sound like a SF
SR--no matter how much you twiddle the Bass knob.
> > > > > Depending on the type of by-pass and coupling caps that sit in the subject SF Super Reverb, few to
> > > > > all may need replacing because of value changes.
> > > >
> > > > Those things are far more durable than you would expect, even after
> > > > 30-40 years.
> > >
> > > I don't care how old they are. I measure 'em all. If they are off value, they are out of the amp.
> >
> > If they're out of spec--sure. But that's rarer than you'd think--even
> > on a decades-old amp.
>
> Not by my experience.
It is by mine.
> How many kathode caps have you measured from the amps of long ago still on spec?
We're discussing coupling caps. Electrolytics are much more likely to
go south. But keep trying to move those goalposts,
Rich!!!!!!!!!!!!!!!!!!!!
>
> http://www.timeelect.com/eh-150.htm
>
> http://www.timeelect.com/vinfpa.htm
>
> http://www.timeelect.com/vinchamp.htm
>
> http://www.timeelect.com/concert.htm
>
> Coupling caps too.
Far more rarely than electrolytics.
> ALL of the caps from the old days age and drift.
Many drift barely at all. That's why you see loads of BF amps with the
original coupling caps. And they sound great.
>
> Like I said. I measure 'em all. If they are off value, they are out of the amp.
They'd have to be off by more than 20% for me to even consider it,
unless they're inducing noise.
> Depending on the type of cap, the value, type of circuit they are in.... temperature is also a
> factor in drift.
>
> Did you know that?
Duh.
Did you know that tubes get hot when you pass a current through the
filament? It's AMAZING!!!!!!!!!!!!!!!
>
> > > > > Slap both bias adj and bal into the amp.
> > > >
> > > > If you don't mind fiddling with that. As long as you use closely
> > > > matched tubes, the bias adjust control is all you really need.
> > >
> > > Not if you want to feed the amp Polished Turds.
> >
> > A lot of new tubes suck. But a lot of new tubes can also be bought
> > closely matched--and stay that way. No great need for a balance
> > control.
>
>
> Well, if what you are saying is absolutely true... why have an adjustable bias control at all.
Because it lets you use totally unmatched pairs of tubes. Handy in a
pinch, but not crucial for most.
>
> These tubes today that you say are manufactured so perfectly to stay MATCHED... they should all
> therefore have equally a matched starting points in their life time too. RIGHT?
>
> So, there is no need for ANY bias adjustments or re-adjustments EVER!
There's always a need for bias adjustments on occasion. SOP.
>
> But then, there is the common mistaking notion that, it is the bias supply itself, that is the REAL
> cause of any tube drifting problem in the equation.
Some tubes drift, some more than others. But you can get current-
production tubes that start out matched and stay close enough over the
course of their lifetime. A bias-balance control isn't a strict
necessity, which is why they're not common.
>
> > > > > I like the AB763 PI ckt.
> > > >
> > > > Much preferred.
> > > >
> > > > >
> > > > > I'd use only the 5AR4. (I use SI diodes in mine)
> > > >
> > > > Not an option with most SF amps. The B+ voltage winds up being too
> > > > high.
> > >
> > > Too high? Well, I guess I never saw it as a problem of any kind.
> >
> > Not if you like hard, sterile tone. I guess some people ain't that
> > particular!
>
> There is nothing sterile of hard sounding about an Ampeg VT-40.
>
> Yet, there is 600 volts on the plates of the two 7027 tubes in that amp.
Not a 6L6GC, which is used by a Fender Super Reverb. Please see the
title of the thread.
Do you have A.D.D., Rich?
> Didn't know that, did ya.
That 7027's are not 6L6GC's? I am well ware of that.
> Then, there is nothing hard and sterile about a well set-up 1971 Super Lead with 535 volts B+
> sitting on the plates of some nice Mullard EL-34's running on the warm side.
Um--also not a 6L6GC, and not a Fender SR. Next?
> But, what you are going to object to is the FACT that, this amp is a HIGH PERFORMANCE *STAGE* AMP
> and is over kill for your common bedroom, garage, and small club venues.
Irrelevant...
>
> Using this 1971 Marshall JMP at the LOWER desired volume levels, you are naturally going to conclude
> in error that, this great sounding HIGH PERFORMANCE *STAGE* AMP is now hard and sterile sounding
> because of it's high voltage.
Also irrelevant...
>
> It's kind a like using a top fuel dragster to go food shopping and complaining about snapping your
> neck every time you touch the gas pedal, having concluded that too much nitro entering the engine is
> the problem.
What does this have to do with a SF SR and 6L6GC's, exactly?
>
> > > > > Also,... GE, Sylvania, or RCA for tubes.
> > > >
> > > > Well, that goes without saying! Telefunken, Mullard, and Amperex will
> > > > do in a pinch.
> > > >
> > > > >
> > > > > After this is done, the suppression caps are pulled, and lead dress is the final move.
> > > >
> > > > Many of the SF amps--at least earlier ones--don't really need lead
> > > > dress adjustment, but it can't hurt. Some of the later 70s amps are a
> > > > mess.
> > > >
> > > > >
> > > > > If I gave this more thought, I may find some things to add I may have forgotten in the throw
> > > > > together post.
> > > >
> > > > You forgot about adding a dash of mojo. Doesn't sound the same without
> > > > it.
> > >
> > > Actually, I rip out the boost ckt, and leave the master volume ckt in most of the Super Reverbs that
> > > leave the shop.
> >
> > Not a big deal. Having an MV pot in there is much less of an evil than
> > having B+ that's 100V too high.
> >
> > --E
Well, Rich, if you could stay focused on a topic, you might eventually
catch on!
--E
Ether
Stephen Cowell wrote:
> "Ether" <et...@x-mail.net> wrote
> > Stephen Cowell wrote:
>
> ...
> >> Any SF with stranded wiring will need re-wiring... unless
> >> you want to leave the supressor caps in. You can't do
> >> lead dress with wire that won't stay where you put it.
> >
> > Many of the SF amps--at least earlier ones--don't really need lead
> > dress adjustment, but it can't hurt. Some of the later 70s amps are a
> > mess.
>
> Early SF had solid wire... my '68 Twin does, FI. Yanking
> the suppressors is a crapshoot, especially with stranded wire
> moving around in there.
Like I said, it depends most on the inital lead dress quality,
regardless of type of wire.
>
> > It doesn't matter what kind of wire was used if it's already in the
> > right place. If the
> > wire is in the right place, you don't need the suppressor caps.
>
> The point is, solid wire stays where you put it. Stranded
> doesn't... unless you go to *great* lengths to tie it back,
> etc. Much easier to just rewire the thing in solid... looks
> cooler too.
Big investiment in time, often not required.
>
> >> This *is* the hard-to-define 'mojo' part... magic.
> >> Throw in a John The Conqueror root and a black
> >> cat bone...
> >
> > Not really. Physics is physics. Either the circuit oscillates
> > uncontrollably, or it doesn't.
>
> ... or it oscillates only on voltage peaks.
That would fall under the category of "It oscillates."
> There's a whole
> continuum of parasitic effect, from not at all to RF CW
> transmitter.
The only part of the contiuum that matters in a guitar amp is the part
where it's not oscillating at all, or at least not enough to cause a
problem. Everything else on that continuum is "It oscillating." If you
pull the supressor caps and you don't see an oscailation problem,
you're set--solid wire or no.
--E
> .
Stephen Cowell
"Ether" <et...@x-mail.net> wrote
> Stephen Cowell wrote:
>> "Ether" <et...@x-mail.net> wrote
>> > Stephen Cowell wrote:
>>
>> ...
>> >> Any SF with stranded wiring will need re-wiring... unless
>> >> you want to leave the supressor caps in. You can't do
>> >> lead dress with wire that won't stay where you put it.
>> >
>> > Many of the SF amps--at least earlier ones--don't really need lead
>> > dress adjustment, but it can't hurt. Some of the later 70s amps are a
>> > mess.
>>
>> Early SF had solid wire... my '68 Twin does, FI. Yanking
>> the suppressors is a crapshoot, especially with stranded wire
>> moving around in there.
>
> Like I said, it depends most on the inital lead dress quality,
> regardless of type of wire.
The plastic wire moves around... the solid
wire stays where it's put.
>> > It doesn't matter what kind of wire was used if it's already in the
>> > right place. If the
>> > wire is in the right place, you don't need the suppressor caps.
>>
>> The point is, solid wire stays where you put it. Stranded
>> doesn't... unless you go to *great* lengths to tie it back,
>> etc. Much easier to just rewire the thing in solid... looks
>> cooler too.
>
> Big investiment in time, often not required.
It makes the amp worth a *lot* more, IMO.
>> >> This *is* the hard-to-define 'mojo' part... magic.
>> >> Throw in a John The Conqueror root and a black
>> >> cat bone...
>> >
>> > Not really. Physics is physics. Either the circuit oscillates
>> > uncontrollably, or it doesn't.
>>
>> ... or it oscillates only on voltage peaks.
>
> That would fall under the category of "It oscillates."
Ah, a new category, that you didn't mention
before. This category includes amps that
don't evince problems until driven hard...
where most folks expect a BF Fender to
shine. This is the big problem... it works,
but not well. Home volume OK, gig volume
poo. IMO everything should be done to
reduce the possibility of parasitics, yet keep
true to the original BF sound. Plastic wire
doesn't fit in with this scheme... to truly
BF an amp it should be rebuilt with solid
wire, and the lead dress tweaked. This is
hard, and you'll have to charge more for
a 'true' BF job... but it's esthetically more
pleasing as well. It just *looks* better.
>> There's a whole
>> continuum of parasitic effect, from not at all to RF CW
>> transmitter.
>
> The only part of the contiuum that matters in a guitar amp is the part
> where it's not oscillating at all, or at least not enough to cause a
> problem.
*Any* oscillation causes problems... it either
sounds sweet all the way up, or you reach a
point where it screeches and sounds bad.
> Everything else on that continuum is "It oscillating." If you
> pull the supressor caps and you don't see an oscailation problem,
> you're set--solid wire or no.
That would depend on how close you look!
__
Steve
.
Rich Koerner
Let's cut to the bottom line here.
Are you saying a 70 Super Reverb CAN NOT produce BF tone.
High voltage being the factor.
Yes or no.
<SNIP OF THE EARS DON'T LIE TEST CRAP>
> Give a listen to several Fender amps from 1964-1978 or so. As the
> years wore on, Fender kept increasing the PT voltage--and plate
> voltage--to increase wattage and clean headroom. And as the years wore
> on and the plate voltage increased, the tone got worse. That's a major
> reason why blackface amps are in such demand. Yes, there are other
> design issues that we've covered--PI coupling cap value, etc.--but in
> many of the Fender amps, the output tube plate voltage has the biggest
> effect on tone.
BS!!!!
You line up all the front end stages, the ass end is a snap.
You guys can't handle making the parts value changes to get that to happen.
So, it can't be done is your conclusion.
>
> >
> > Here are the specs common to those tubes used in amp design.
> >
> > http://www.timeelect.com/6550ap1.gif
> > http://www.timeelect.com/6550ap2.gif
> > http://www.timeelect.com/6550ap3.gif
> > http://www.timeelect.com/6550ap4.gif
> > http://www.timeelect.com/6550ap5.gif
> > http://www.timeelect.com/6550ap6.gif
> > http://www.timeelect.com/6550ap7.gif
> > http://www.timeelect.com/6550ap8.gif
> >
> >
> > This tube data represents what the vacuum actually does.
>
> Why are you posting links to 6550's when we're discussing a SF SR,
> which uses 6L6GC output tubes? Sure, if you want to change the design
> and equipment, you can get all kinds of different results. Don't move
> the goalpaosts on us, Rich!!!!!!!!!!!!!!!!!!!!!!!!!!
Because I don't have the time to scan and process the same looking curves you will see for a
GE-6L6GC.
> > Point out the *tone suck points* you are talking about on the operating curves supplied, and I'll
> > show you a tube/s performing at improper operating points.
Then, you can point to those same suck points on those GE-6L6-GC curves too.
>
> Ignore your 6550 curves, Rich, and lets get back to the 6L6GC. As you
> yourself have said, every tube has its "sweet spot". For 6L6GC's in a
> Fender circuit, that sweet spot is well south of 500 volts, and
With all the front end stages running at BF voltages, the 500 volt sweet spot established.
> probably closer to 450V. As you get near 500V and beyond, the tone
> gets hard and brittle. That's why those Fender-like Music Man amps
> with the high plate voltages sounded like crap.
Oh, the SS front end and kathode drive CKT would have no influence on your ears either for the error
in your conclusion.
> > High voltage is NOT the cause for bad tone.
>
> In a SF SR, it sure as hell is.
>
> > Improper tube operation and/or application IS.
> Right--like running a 6L6 at over 500V in a Fender circuit.
If you are *NOT* pushing that BF Super Reverb into output stage clip and/or the OT *NOT* into core
saturation, and are doing the same on a 500 volt Super Reverb to the same output level, of let's say
35 watts,..... given identical 9 pin tube function on BOTH Super Reverbs... WHY would they NOT
sound the same with only a 50 volt different on the 6L6's?
<SNIP 2 save space>
> They'd have to be off by more than 20% for me to even consider it,
> unless they're inducing noise.
20% can make a difference in a side by side when the tone pot is at the end of its rotation.
Especially, when that cap is located up stream a few stages from the EQ ckts.
<Another space saving snip>
> > > > > > I'd use only the 5AR4. (I use SI diodes in mine)
> > > > >
> > > > > Not an option with most SF amps. The B+ voltage winds up being too
> > > > > high.
> > > >
> > > > Too high? Well, I guess I never saw it as a problem of any kind.
> > >
> > > Not if you like hard, sterile tone. I guess some people ain't that
> > > particular!
> >
> > There is nothing sterile of hard sounding about an Ampeg VT-40.
> >
> > Yet, there is 600 volts on the plates of the two 7027 tubes in that amp.
>
> Not a 6L6GC, which is used by a Fender Super Reverb. Please see the
> title of the thread.
Hold a Sylvania 7027 and Sylvania 6L6-GC next to each other.
Their specs are almost the same with a different pin out.
Ether
I was very clear. A '70 SR will be much easier to convert to blackface
than a later '70s UL SR. If you want blackface tone, it's not worth
the effort and expense to convert a UL SR.
I'm speaking English, Rich--are you?
> High voltage being the factor.
>
> Yes or no.
Yes--high voltage on the 6L6GC plates is the major factor here, all
else being equal. The UL PT puts over 500V on the plates. A BF SR will
be around 50-60V lower. For a 6L6GC, that's a critical 50 volts.
> <SNIP OF THE EARS DON'T LIE TEST CRAP>
T'aint crap, Rich. The ears test is the only one that matters.
Otherwise, we'd all be using SS amps. And nobody would care about BF
Fenders.
>
> > Give a listen to several Fender amps from 1964-1978 or so. As the
> > years wore on, Fender kept increasing the PT voltage--and plate
> > voltage--to increase wattage and clean headroom. And as the years wore
> > on and the plate voltage increased, the tone got worse. That's a major
> > reason why blackface amps are in such demand. Yes, there are other
> > design issues that we've covered--PI coupling cap value, etc.--but in
> > many of the Fender amps, the output tube plate voltage has the biggest
> > effect on tone.
>
>
> BS!!!!
So--why do people prefer the tone of the BF and early SF Fenders?
Hmmmmm. And why doesn't a throughly blackfaced early-SF SR sound quite
as good as a BF SR? Hmmmmmm. Could it be that putting a 5AR4 in a SF
SR cranks the plate voltage up too high?
Bingo!
> You line up all the front end stages, the ass end is a snap.
Only if you're not that picky about tone. Some ain't.
> You guys can't handle making the parts value changes to get that to happen.
Sure you can change as many parts as you want--including the required
PT change. Which = $$.
> So, it can't be done is your conclusion.
Anything can be done. Is it worth the effort and expense to blackface
a UL SR? No. Not unless your parts and labor are free.
> >
> > >
> > > Here are the specs common to those tubes used in amp design.
> > >
> > > http://www.timeelect.com/6550ap1.gif
> > > http://www.timeelect.com/6550ap2.gif
> > > http://www.timeelect.com/6550ap3.gif
> > > http://www.timeelect.com/6550ap4.gif
> > > http://www.timeelect.com/6550ap5.gif
> > > http://www.timeelect.com/6550ap6.gif
> > > http://www.timeelect.com/6550ap7.gif
> > > http://www.timeelect.com/6550ap8.gif
> > >
> > >
> > > This tube data represents what the vacuum actually does.
> >
> > Why are you posting links to 6550's when we're discussing a SF SR,
> > which uses 6L6GC output tubes? Sure, if you want to change the design
> > and equipment, you can get all kinds of different results. Don't move
> > the goalpaosts on us, Rich!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> Because I don't have the time to scan and process the same looking curves you will see for a
> GE-6L6GC.
>
> > > Point out the *tone suck points* you are talking about on the operating curves supplied, and I'll
> > > show you a tube/s performing at improper operating points.
>
> Then, you can point to those same suck points on those GE-6L6-GC curves too.
I believe I already did--i.e. close to 500V and above, no matter what
the bias. Hard and brittle.
> >
> > Ignore your 6550 curves, Rich, and lets get back to the 6L6GC. As you
> > yourself have said, every tube has its "sweet spot". For 6L6GC's in a
> > Fender circuit, that sweet spot is well south of 500 volts, and
>
>
> With all the front end stages running at BF voltages, the 500 volt sweet spot established.
English, please...
But 500V plate voltage is too high for the best tone in a BF SR with
6L6GC finals.
By the way--the Marshall Super Lead with 500V on the plates doesn't
sound as good as the 50-watt JMP with 400 volts on the EL34's. The 50-
watt 400V JMP is sweeter.
>
> > probably closer to 450V. As you get near 500V and beyond, the tone
> > gets hard and brittle. That's why those Fender-like Music Man amps
> > with the high plate voltages sounded like crap.
>
> Oh, the SS front end and kathode drive CKT would have no influence on your ears either for the error
> in your conclusion.
Sure, there are other differences in the MM amps that make them
inferior to Fenders. But they're closer in tone to a UL SR than to a
BF SR, and a lot of that is the high plate voltage.
>
> > > High voltage is NOT the cause for bad tone.
> >
> > In a SF SR, it sure as hell is.
> >
> > > Improper tube operation and/or application IS.
>
> > Right--like running a 6L6 at over 500V in a Fender circuit.
>
> If you are *NOT* pushing that BF Super Reverb into output stage clip and/or the OT *NOT* into core
> saturation, and are doing the same on a 500 volt Super Reverb to the same output level, of let's say
> 35 watts,..... given identical 9 pin tube function on BOTH Super Reverbs... WHY would they NOT
> sound the same with only a 50 volt different on the 6L6's?
Because that 50V pushes the 6L6GC out of its sweet spot.
Consider the BF and SF Fender Champ, single 6V6GT final. The PT on a
BF Champ puts out around 330V, right? Plate voltage at around 350V.
Pretty good tone, right? Now, fast forward to the late 1970's. Same
amp design, same component values--except the PT is now cranking out
more voltage, and the plate voltage is north of 410V. AND it just
doesn't sound the same! The preamp voltages aren't really that far
off, but the plate voltage is now out of the "sweet spot" for a 6V6.
Too high, hard and brittle tone.
> <SNIP 2 save space>
>
> > They'd have to be off by more than 20% for me to even consider it,
> > unless they're inducing noise.
>
> 20% can make a difference in a side by side when the tone pot is at the end of its rotation.
> Especially, when that cap is located up stream a few stages from the EQ ckts.
Considering that the original cap values were all over the map when
installed, and those old BF Fenders sounded good anyway, you'd be
crazy to remove the original caps unless they were way off or noisy.
> <Another space saving snip>
>
>
> > > > > > > I'd use only the 5AR4. (I use SI diodes in mine)
> > > > > >
> > > > > > Not an option with most SF amps. The B+ voltage winds up being too
> > > > > > high.
> > > > >
> > > > > Too high? Well, I guess I never saw it as a problem of any kind.
> > > >
> > > > Not if you like hard, sterile tone. I guess some people ain't that
> > > > particular!
> > >
> > > There is nothing sterile of hard sounding about an Ampeg VT-40.
> > >
> > > Yet, there is 600 volts on the plates of the two 7027 tubes in that amp.
> >
> > Not a 6L6GC, which is used by a Fender Super Reverb. Please see the
> > title of the thread.
>
> Hold a Sylvania 7027 and Sylvania 6L6-GC next to each other.
>
> Their specs are almost the same with a different pin out.
Almost?
--E
Ether
--Sigh---
Steve--please look up "binary number system" on Google.
1=Yes
0=No
Any flavor of problematic oscillation would fall under "1". An
absence of such would fall under "0". That's all that really matters.
You can use old chains for your wiring as long as the amp doesn't
oscillate.
--E