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Help needed from the Quad-6V6 guys!

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3/14/2000 1:23 AM

Help needed from the Quad-6V6 guys!

I know a number of you have built amps
with a quad of 6V6's for output. I'm
currently working on one almost exclusively
based on the Tweed Twin 5F8-A circuit.

What I'm considering modifying is the tone
stack. I want to eliminate any dead spots
or useless settings and maybe narrow the
range on the bass/mid/treble settings.
My rationale is that this will eliminate
useless extreme settings (like knobs on 10
or 0) and allow me to make the tone
controls more capable of subtle changes
within a limited, more useful range.

So I need the opinions of anyone who has
used 6V6's in tweed-style circuits (like
the Bassman 5F6-A or Twin 5F8-A, etc.).
Are there any dead spots or useless
extreme settings that I can eliminate?
Do you really need a bass or mid or treble
that goes from 0 to 10 or is a more
limited range acceptable for any or all
of these controls? ANY opinions welcome!
Thanks!
TJK

3/14/2000 1:47 AM
Nigel T.	0-10? hah. Ours go to eleven.

3/14/2000 4:51 PM

Check out Randall's article on tone control scaling at http://www.aikenamps.com.

I don't quite understand what you are getting at. I mean, the numbers are just a convenience so you can remember where you were when you "dialed it in". The full range of the pot can be scaled to have less overall effect, but unless the amp is going to be used with only one specific guitar, you can't really be sure that an extreme setting for one guitar will be extreme for another. Light woods, dense woods, hollow bodies, single coils, humbuckers, EMGs/active pickups - there's quite a range of possible input tones.

I apologize if this isn't entirely useful. Somebody else may have some more specific values for you, but I think, really, if you want to vary or customize the Fender tone stack to your purposes, you'll probably need to experiment. You could get a sub box to easily switch between different cap values.

If your question is more about modding the tone stack to "compensate" for the difference in tone between the 6l6s and the 6v6s, compare the tone stacks of a two 6l6 amp vs. a two 6v6 amp. They are basically the same. In a way, the tonal difference between 6l6s and 6v6s is negligible. Their dynamic response is quite different though which gives them each their character. You would have more success playing with the presence control/feedback for this as it directly affects the way the power section works.

steveR

3/14/2000 6:45 PM

A little clarification...

I guess I wasn't exactly clear on what I'm
looking for so I'll try to clean it up a
little.

Certain amps I've owned (Blackface Fenders,
for example) tend to have certain max/min
settings I'll never use. For example, I'll
never set bass to 10 on a cranked BF Fender,
so that high side of the potentiometer is
basically useless in the amp. So what I want
to do is add some resistors and smaller-range
potentiometers into the circuit so that
instead of having a knob that functions as
a normal bass knob (0 to 10), I now have a
knob that effectively works in the old range
of 2 to 8. I can now dial in a smaller range
of tones but have more control over it (the
difference between 5 and 6 on my new knob is
the same as the range between 5.2 and 5.3 on
the old knob -- just easier to dial in).

My reasoning is that while old designs are
pretty versatile, they don't need to be
THAT versatile once you've settled on a
particular guitar set-up for a specific
amp. I know it's going to take some fine
tunings, but I was just checking with
some of the guys out there who have
basically built the same amp I'm building
(I know there's at least two 4-6V6 amps
based on tweed circuits built by guys
here) and see what their experience is
so far. I know I'm going to do a lot of
experimenting, but I was hoping a few
general pushes in the right direction
could help me keep an eye open for certain
things.

Thanks for the input though!
TJK

3/14/2000 9:05 PM
jason	If your bass pot is normally 1M you could try a 500K with a 250k resistor in series with it on each end. You still have 1M between the mid and treble pot. Because of the taper of the pot it may not be as simple as 250k on each end. You'll probably need to play with the values some to find the combo that works in the range you want but the idea is still the same. Did any of that make sense? jason

3/15/2000 1:55 AM

Yeah, that makes sense and that's kind of
the idea I was going with. I was wondering
if anyone had any more specific values/
settings that I could use to get a better
idea of what resistor-pot combo to start
with but either the tweed-quad-6V6 guys
aren't biting or their amps just sound
great at any setting -- could be the
latter! I'll just experiment and do it
the hard way! Thanks for all thoughtful
responses.
TJK

3/15/2000 9:43 AM
Nils	Todd, I've built a 5F6A-circuit with 5881's and used the D-word tone section. I think that it's quite easy to tinker with, it's sort of more dedicated to each pot and easy to get useful ranges. Nils

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