Fender 350k tapped treble pot

[Fred G.]

I've never had the opportunity to play any of the old Fender amps utilizing this. I'd like learn a little about it...

Can somebody give me a rundown on what effect this particular pot has, in terms of both function and sound-wise?

Thanks in advance,

Fred G.

[AdmiralB]

It shunts a little bit of the high end (from the bass and mid portion of the tone stack) to ground. I've played amps with it...some nice, some I didn't care for...but the only times I've swapped them in and out with regular 250K pots, I can't tell any difference.

[Fred G.]

Thanks, Admiral.

So that's all it does, huh? I have always wondered about those pots. Nice to know now that I won't want to fork out any cash to try one out!

Thanks again - I appreciate the info.

Fred G.

[AdmiralB]

That's all it does in that circuit. You'd get identical results with a 280K pot (OK, 250K), and a 70K resistor (OK, 68K). Connect the resistor on one end to the bass pot/treble pot junction and on the other to a .0033uF cap to ground.

[bob p]

FYI, Kelley Brown's schematic for the Transatlantic Bassman uses the methods you've mentioned to simulate the whiteface tone controls. You can google the schematic.

[AdmiralB]

The only situation in which that won't work is if you turn the treble down past the 'tap' point...but I can't imagine that many people do/did.

[Thorny]

Weber VST used to have those pots - and they were reasonably priced. I haven't checked recently.

[PRNDL]

The tapped pots were used for James (Baxandal) tone controls

The James circuit was used for hifi amps primarily because it has a flat frequency response with the treble and bass at 5. Increasing the treble and bass resulted in a mid-scoop similar to the Fender/Marshall tone controls.

The story is that Fender got a bunch of these pots from a HiFi amp builder that went out of business. He used them for a little while and then switched back to the standard circuit.

The attached schematic is for a 6g8 twin.