Who sells 350k pots with 70k taps?

[tubeswell]

(Treble pot for 6G5-A/6G6-B/6G9-B etc)

- Or will a 250k pot with a 68k resistor in series off the ground leg work the same sort of way? (with the junction being the 'tap'?)

[Daver]

You can get them from Ted Weber (RIP). https://taweber.powweb.com/store/potsord.htm
The body is smaller than vintage pots, but they work as advertised.
Dave

[txstrat]

Watch out, the shipping might be way more than the pot (at least it was to my location).

Although I must say the pots work great you could try to use a standard 250k pot and add a 68k or 82k resistor in series with a .003 cap to ground from the bottom tap of the pot.
I used a .0047 cap here 'cause I was tinkering with a 6g11 circuit.

[tubeswell]

Yeah at the moment there's several of brown amps with interesting tone stacks that have my curiosity, so maybe I should order a bunch of those pots from Weber. :-)

The brown Twin looks interesting, so do the blonde Bassman and Tremolux. Also the later brown Concert, Pro, Showman, Super, Vibrasonic, Vibrolux with the zany looking harmonic vibrato circuits look fascinating. Wonder what they sound like?

[txstrat]

My latest build was a Vibrolux 6g11 clone (at least the first channel) and I had tone (disharmonic distortions) issues I discussed here in the forum. Tried the 250k pot instead of the 350k with 70k tap.
Frankly, I noticed no big difference. The 350k pot sounds a little 'darker' to me than the 250k.

[tubeswell]

My latest build was a Vibrolux 6g11 clone (at least the first channel) and I had tone (disharmonic distortions) issues I discussed here in the forum. Tried the 250k pot instead of the 350k with 70k tap.
Frankly, I noticed no big difference. The 350k pot sounds a little 'darker' to me than the 250k.

Interesting. What were your voltages like?

[txstrat]

Well, I don't remember exactly but it was just under 400vdc at the plates and 1 or 2 volts less at the grids (470 ohms 2w resistors).
In the end I put the 350k back in and turn it up to around 3 o'clock. In my other builds (250k pot) I usually turn the treble up to 1 o'clock. Just to give you a picture how I set the amps.

[JoeM]

txstrat,

You have 2 .0047 caps in the circuit. Should the one that connects to the 6800 ohm resistor actually be .047uf?

[txstrat]

Oops, that's right.
What to say, copy and paste
Here's the right schem.

[TheTinMan]

Doug Hoffman was nice enough to get some of those tapped pots when I asked if he could make them available: Tube Amp Pots and Knobs

I really liked the Brown tonestack on the Normal channel of my Super Reverb build.

Chip

[tubeswell]

That pot looks like it says "70% tap". I thought the brown amp treble pots had a 70k tap? or what?

[txstrat]

I thought the brown amp treble pots had a 70k tap? or what?

You're right.
The pot in the pic (on the Hoffman site) looks like those I ordered from Weber. Only 15mm wide. The pots of the brown fender amps had indeed a 70k tap not 70%. I can imagine the pots on the Hoffman site are the same. I've never heard of pots with a 70% tap. I tend to believe they just mixed up 70k and 70% for some reason.

[TheTinMan]

I'm almost certain that Hoffman got his pots from the same place as Weber, if not from Weber directly. I measured the values on the pot I received but am away from home for a few days and can't check right now.

Chip

[txstrat]

I've checked my spare pot for the values.
350k from input to output. 60k from input to tap. In between 60k and 290k from wiper to tap. 290k from output to tap.
Although that's not the stated 70k I think it's well within the limit.

[TheTinMan]

Actual values

The tapped pot I got from Hoffman measured 313K from end-to-end and the tap was 56K from the "bottom" leg.

Chip