Fender 350k tapped treble pot

Fred G. · 03-06-2007, 06:01 PM

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 · 03-31-2007, 01:54 AM

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. · 04-01-2007, 10:57 PM

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 · 04-01-2007, 11:01 PM

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 · 04-03-2007, 04:05 PM

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 · 04-03-2007, 04:39 PM

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 · 04-07-2007, 09:22 PM

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

PRNDL · 05-05-2007, 07:53 AM

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.

03-06-2007, 06:01 PM	#1
Fred G. Member Join Date: May 2006 Posts: 78	Fender 350k tapped treble pot 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. Last edited by Fred G.; 03-06-2007 at 08:36 PM.

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03-31-2007, 01:54 AM	#2
AdmiralB Member Join Date: Jun 2006 Posts: 102	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.

04-01-2007, 10:57 PM	#3
Fred G. Member Join Date: May 2006 Posts: 78	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.

04-01-2007, 11:01 PM	#4
AdmiralB Member Join Date: Jun 2006 Posts: 102	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.

04-03-2007, 04:05 PM	#5
bob p Senior Member Join Date: May 2006 Location: What's left of NW Indiana Posts: 1,072	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.

04-03-2007, 04:39 PM	#6
AdmiralB Member Join Date: Jun 2006 Posts: 102	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.

04-07-2007, 09:22 PM	#7
Thorny Member Join Date: May 2006 Posts: 56	Weber VST used to have those pots - and they were reasonably priced. I haven't checked recently.

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