Connecting two circuits to the same pot?

[jtrezzo]

Basically I have two different Big Muff circuits, and it would be nice to just put them in the same box with a DPDT on the in and outs. If I connect both wires from the two PCBs to a single gang pot will it work right? Or is there something that will change the value? Would dual gangs be necessary?

[induction]

Out of curiosity, why do you want to do this?  Are the two circuits different, or do you just want two identical circuits with different settings?  If they're different circuits, you might be able to get away with just switching out the part of the circuit that's different.

Assuming you've already built both circuits, I suggest you switch the inputs in front of the pulldown resistors (just like true bypass switching), and switch the outputs between the output cap and volume control. Put a pulldown resistor after the output caps to prevent popping.  The (single gang) volume knob can be shared, but you probably don't want both circuits attached to it at the same time.

I recommend you try it on the breadboard first to make sure it does what you want and doesn't pop.  It wouldn't be any harder two switch the entire circuit including the volume knob, which might be better or not, depending on what you're trying to accomplish.

[jtrezzo]

Yes they are two different Big Muff variants. What I want is to have them both switchable on a DPDT switch (which I have done before with something else, though with separate pots) but was just wondering if they can share the same pots without any effect on the sound i.e. have Vol 3 from Big Muff A and Vol 3 from Big Muff B on lug 3 of one pot and so on. I guess what I want to know is if somehow having the two connected to the same lug would have some mathematical effect on the whole equation and change the sound at all.

[induction]

If both circuits are attached to the volume pot at the same time, then yes it will affect the sound.  But if you wire it like the picture below, only one circuit is attached to the pot at any given time, and you won't have a problem.

The input pulldowns and output caps are in the circuits already (at least in the standard BMP circuit, I don't know about your variations), but you'll have to add the output pulldowns.