2 knob tone stack

[EFK]

Can someone give me any idea why the treble pot in the tone stack shown attached (from a Selmer TNB) doesn't really seem to do much? I don't just mean on an old amp - not a bad pot issue or anything - I mean in practice, built w/ new pots etc. Treble knob really doesn't have much effect. Values are 100K(B) treble and 250K(A) bass.

Also, how does this tone stack effectively differ from the Fender brownface shown here, which puts the cap above the bass wiper as opposed to spanning it as per the Selmer:

Adam's Amplifiers: Tone Stacks

Finally, is there some reason one would not want to convert this over to a Baxandall in this circuit (Selmer) - i.e., more signal loss than stock etc.

Thanks!

[Steve Conner]

What? I had a Selmer TnB 50, and the treble knob works fine.

[pdf64]

The turnover frequency of that circuit is higher than the regular fender values - 220pf into 100k cf 250pF into 250k.
If the treble cap is replaced with a 470pF, does it perform more as expected?
Though it's not clear which fender tone circuit you're refering to?

[EFK]

Well, I don't mean it doesn't work at all. It works, just not very dramatically. It's a fairly subtle treble control. Fairly subtle bass control too but the changes within the range of the bass pot are more noticeable.

Two things I'm mostly curious about: if you click the Adam's Amplifiers link above, is diagrams of the Fender 6G5 or 6G7 should pop right up. If I'm comparing them correctly *values aside*, the Selmer and the Fender differ in the placement of the cap between the treble and bass pots? Maybe they're effectively the same, I'm not sure, but I think there's a difference. If so, I'd like to know what that practical difference would be: there doesn't seem to be a way to model this stack in Duncan's calculator?

Also: would there be any reason NOT to use a Baxandall in this circuit? Is it going to suck too much signal? Or any other problem?

I'll try some different treble cap values and see if there's a noticeable difference.

[pdf64]

'the Selmer and the Fender differ in the placement of the cap between the treble and bass pots? Maybe they're effectively the same'
Yes, I reckon that the equivilant circuits are the same, Selmer and Fender.
Fender max bass with wiper at ground.
Selmar max bass with wiper up at the treble pot node end of the track.
It's just the way they're drawn.
However, that 6G7 Fender circuit will operate like the Vox tone stack, in which max bass cuts the mids out.
It would be more intuitive not to ground the bass track end, so that the bass pot doesn't affect the mids.
I think that's what you are refering to, sorry if I'm barking up the wrong tree.