switchable tone stack settings sans pots ?

[walkman]

Hi,

i just built a champ like amp out of an old valve radio , line up is a 6aq5 and
two 6av6. It could be the sound of the 6aq5 is much preferable to my ears than an el84 , which i have used in other efforts, but it seems to be my bestbuild so far.

There is no tone stack yet and no attenuation between the 6av6 , both have bypass caps the first 25 uf and the second 1 uf . What id like to do is add a mid cut or mid control to cut 400hz by about 5 or 6 db, and 800hz by about 3 or 4 db. Perhaps + 1 or 2 db at 3khz and a optional cut on 100 or 200 hz of the same. Ie these are settings on an eq pedal that i put before the amp.

Now the amp sound great with a low output single coil, but is too muddy with a high output humbucker. So the thought was for a switchable setting or preset so that the amp can be in a single flick suited to one type of guitar or other.

Perhaps bright switches on the input or across the volume could be better, or swtchable cathode bypass caps as well . Well its bound to trial and error for sure, and the easiest way is to start with standard designs , tweed or blackface etc.

Are there any designs out there that go without pots for tone stack settings? Perhaps that could use a single setting rotary switch to change between types and or positions of the stack, again these having set values rather than pots

phew thats a lot to ask........

the trainwreck designs look interesting ... perhaps i should study them.....
its more rewarding actually getting down to working on the amps than condensing info , so suggestions please....

what direction would you go to get some useful tinkering done.

cheers

walkman

[Don Symes]

Trainwrecks, Matchlesses and some Oranges use rotaries to play with coupling cap values as a means of tone control.

Your thinking is sound, but with no pots, you're going to be doing a painful amount of de/soldering to find the value sets you want.

How about a bank of trimpot-controlled 'stacks that you select with a rotary?
You get exactly what you want and your settings are safe from idle/drunk twiddlers.

Hoep this helps!

[Enzo]

Other than just to be able to say it has none, why are we so set against pots in the EQ? You can always put a resistor in place of a pot - or two resistors - and the switch the resistors in and out. Seems like more trouble than a pot to me.

Is it just "potness" that is the issue? Circuits don't know whether a resistance is a pot or a fixed resistor, all the current sees is the resistance.

[walkman]

nothing against pots per se.... i find i like to have a generally 'bright' sound on the amp and roll down the tone on the guitar to compensate ....

the chassis / case of this old radio is more suited, in my view, to switches rather than pots with its limited space to retainan uncluttered look... and later could more easily be made foot-switchable.

I want the amp to have an overall sound that has a bit of mid cut for single coils and a bit more for humbuckers, perhaps a slightly decreased bass and accentuated treble overall.

Perhaps the tone stack is the wrong place for this , maybe a tweed tone different bypass caps and bright cap's is the way to go?

Whats the best way to calculate to the frequency response of that kind of tweaking ?

How can i compare this to thew settings i like with the eq pedal?

[Enzo]

Go to www.duncanamps.com and check out the free download tone stack calculator. You can play with the values in the tone stack all you like and see the results.

He has other swell stuff there too, like the power supply designer.

I like to think there is voicing the amp and then there is the tone stack. That old Fender or Marshall sounds like a Fender or Marshall no matter what you set the EQ dials to. The EQ lets you adjust the tone, while the rest of things make the amp sound like the amp it is.

In a nutshell, the cathode bypass cap effects gain and bottom end response. Brite caps affect upper end for... brightness. The typical brite cap across a vol;ume control has less and less effect the higher you set the volume control.