Is it possible to make a footswitch switch pots in a pedal

[Jallawalla]

Hi all,

Long time lurker and my experience is pretty small (built one amp and no pedals).

Short version:
I would like to rehouse/mod my pedal with a footswitch to switch between 2 gain and volume pots on my pedal. I have sketched the problem here. I would also like/need an indicator LED to light up when the 2nd set of pots was engaged.

When I think about it, I run out of connections pretty rapidly as I would do it the longwinded way of taking each of the connections from the board to the middle of the switch and then branch off to each of the new pots.

Can any of you work out how this could be done? There seem to be a few commercial pedals that do this.



Long version:
My pedal has 250k gain pot and in the first 10% of the range it sounds very fat and bluesy, very 'low-gain'. At the high end the pedal is a full on distortion, like a wall of marshalls.
a) I'd like more control over the gain by putting say, a 50k pot in the gain position
b) I'd like to footswitch between 2 settings, low gain (50k pot) and high gain (250k pot), but also at different pot settings - I think that I need to have a second vol pot since when I switch to a second higher gain pot the volume will go up too much.
c) I'd ideally like an led if but if not possible then I could live without it (probably).

Thanks for any help you can offer.

[bcalla44]

I think Barry sells what you're looking for over at GuitarPCB.com.

http://www.guitarpcb.com/apps/webstore/ ... ow/3436270

[Jallawalla]

Thanks for the reply.

Just had a good look at that. I have read through the pdf and can't see how I can use it for 2 pairs of pots. It appears to only handle one pair of pots.

I may well be missing something, or is there some way of piggy backing 2 of these boards?

[Nocentelli]

4PDT for LED, 3PDT without. I assume the gain pot goes in the feedback loop of an opamp? Also, by convention, volume controls have lug 1 grounded, lug 2 is output and lug 3 comes from the circuitboard and carries full signal.

I'll post a wiring diagram when I'm on the PC, but essentially one pole switches volume lug 3, one for volume lug 2 (both volume lug1s are permanently grounded), one pole switches between the lug 1s of the gain pots, and the lug 2s of the gain pots are both permanently wired to the correct spot on the board: Whichever gain pot is not in use goes open circuit so does not interfere with the circuit - You can't do that with a pot used as a voltage divider. A fourth pole can be used to switch an LED.

[Jallawalla]

Thanks. Yes - gain pot is in the feedback loop of an opamp . My circuit reading is amateurish, but looks that way to me. (opamp is a 3 connector triangle(?) and there are 2 diodes and a cap running in parallel with the pot in the feedback loop)

Looking forward to the diagram.

4PDT for LED, 3PDT without. I assume the gain pot goes in the feedback loop of an opamp? Also, by convention, volume controls have lug 1 grounded, lug 2 is output and lug 3 comes from the circuitboard and carries full signal.

I'll post a wiring diagram when I'm on the PC, but essentially one pole switches volume lug 3, one for volume lug 2 (both volume lug1s are permanently grounded), one pole switches between the lug 1s of the gain pots, and the lug 2s of the gain pots are both permanently wired to the correct spot on the board: Whichever gain pot is not in use goes open circuit so does not interfere with the circuit - You can't do that with a pot used as a voltage divider. A fourth pole can be used to switch an LED.

[Nocentelli]

I've left the last pole empty for any LED switch scheme you like. You could have a single LED that lights to show high gain mode selected, or two separate LEDs of different colours (e.g. red for high gain, blue for normal), or you could use a single bicolour LED that changes colour to indicate mode.

dual volume+gain switching.gif (17.58 KiB) Viewed 1984 times

[Jallawalla]

Wow. Thanks vety much. Need a bit of time to digest that one.

I'm off to order the bits.