Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jordan86 on January 13, 2021, 10:48:46 am
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I have an AX84SEL amp that a friend built me years ago. It's a high gainer for sure. There are actually two separate gain pots in the circuit, which are wired in my amp on a Dual ganged pot. So the one gain control on the faceplate adjusts the two 500K pots simultaneously to the exact same setting. The tweaker in me really wants to see what it would be like to control them independently. Say Gain 1 Max, Gain 2 low, vice-versa. Would love to avoid drilling the chassis though if I can. The faceplate is custom and really nicely done. Plus I don't want to muck up the work my friend did.
I recall radios and such having pots like this. One shaft, but two parts to it. A front and back that can rotate independently? Or maybe a push pull where Gain 1 is on the in, and gain 2 is on the out? I would still need 6 lugs like a standard dual gang pot.
Anyone know of a pot like that and what it would be called?
I've also thought about bypassing one pot's wiper and just hardwiring one of the controls full on (less surgery), but I've not experimented enough to know which I'd prefer to bypass.
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It's call a dual concentric pot. Of course it requires dual concentric knobs. Here's one...
https://guitarelectronics.com/cts-stacked-dual-concentric-audio-pot-500k-500k/?gclid=EAIaIQobChMI76jTwrCZ7gIV4o1bCh1aYgQ4EAQYASABEgJ_T_D_BwE
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I guess if I wanted to experiment with one control always wide open, I would just need to move that wire from lug 2 wiper to lug 1? Lug 3 to ground. This would bypass the wiper and essentially have that pot at full resistance? Could try it on one, put it back and try it on the other. That wouldn't be too hard.
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It's call a dual concentric pot.
Thanks, Sluckey!
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Find a normal 500K log pot
disconnect the wires from one section of the existing pot
connect the wires to the new pot
now you can experiment easily which will be the effect on having separeted pot control
if you like it buy an appropiate dual concentric pot with knobs
Franco
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I guess if I wanted to experiment with one control always wide open, I would just need to move that wire from lug 2 wiper to lug 1?
Great idea. I do have a spare 500K. If I do like one of the controls always wide open, would this idea of bypassing the wiper lug be a real solution? That would save me buying a $15 pot/knob scenario and rewiring everything.