Heres the deal.
I was wondering if one could use a "std" volume pedal as an expression pedal for diy stomp boxes?
After all its just a pot in a box right?
I have used my volume pedal as an expression pedal before with my little Zoom 505 (old school I know) with a Y cable.
So If i wanted to use the volume pedal as an expression pedal such as part of a resistive divider to vary the speed of an lfo could it be done?
Ergo; Phaser speed? Tremolo Speed?
Btw what value of pot is standard in a volume pedal. If there is a standard.
If not then I guess a 4 poles switch with various sized R on the lfo would do the trick.
Cheer
Rich
I just stuck the meter on the in's, outs
no variable resistances on the ins
but a swing from 18k to 110k on the outputs.
At least I know what i have to work with now.
Same for anyone elses please ?
Depends on the make.
F'rinstance, the Line 6 standard is simply a 0-10k variable resistance to ground. In my old MXR 113 Digital Delay, it was a 50k resistance to ground. In other cases, the expression-pedal input assumes that you'll be dividing down a specific voltage. Source Audio pedals use 3.3V, while others might use 9v or 5V divided down. The voltage that gets divided down might come from the pedal itself, requiring a TRS jack and plug. Where the expression pedal is presumed to come with its own power, there might be a 9V battery in the expression pedal, with a 5V three-pin regulator to provide a stable 0-5V variable control voltage. It may use the pot in the controller as a 3-lug voltage divider, but only a mono hot/ground plug and jack are required at the effect pedal jack.
I have no idea what's most common. Of course, if it's DIY then the choice is yours.
FWIW, once I learned the Line 6 standard was a simple 0-10k, I wired up a photocell to the expression jack input, taped it to the top of my guitar near the volume pot, and "played it" with my pinky.
10k is the most common for the expression pedals meant for things like keyboards and other digital/midi gear. As they are providing a variable voltage, the pot value isn't too critical. The annoying thing that varies are different ways of wiring the TRS. Sleeve usually ground, but tip & ring can be either +V or wiper. To work with a variety of expression pedals, it would be an idea to fit a DPDT slide switch to select which tip/ring type. Because the pot value can vary, it would be wise to use voltage control, or a buffer to to turn it into current control, in the effect.
Working with a guitar volume pedal instead with an in/out adapter cable might be a better approach. The higher value of volume pots might better suit direct control of stompbox circuits, but only if it has a ground at one end. That said, you probably could get away with envelope/LFO (non audio) controls with the sleeve "live" and an isolated TRS socket. Of course, the TRS socket can be like the Cliff/Rean fitted with extra contacts that are made when the plug is out, so a panel control can still be used.
Thanks guys.
I just assumed all volume pedals are the same.
for clarity.
I have a passive 2 in 2 out guitar volume pedal (made in Korea) IIRC sold by JHS back in the 90's
I was thinking of using it (or rather its resistance) as one half of a resistive divider to vary the speed of an lfo.
Sorry for any confusion, I now realise you can get other sorts of volume pedals.
It never even occured to me you could get active ones.
let alone different jack pinouts.
I'll try to do a mock up of what i had in mind. This could lead to even more confusion though :)