Volume Pedal Conversion
recently dug out one of my old ME-6B bass effects pedal boards (I have two because after the first one was stolen I bought a replacement - but then the first one was recovered by the police and returned) and was playing around with it when I decided I wanted to attach an "expression pedal" to it (this would allow me to control the output volume mid-chain - i.e., after some effects but before others). A little Googling revealed that buying a new expression pedal would be ridiculously expensive (~$70 for a pedal attached to a potentiometer and a 1/4" jack?!) (used gear isn't much better, once you factor in shipping) - so I decided I'd make my own. Or, rather, I would re-appropriate some existing hardware.
A number of years ago a coworker gave my a broken volume pedal, which I subsequently fixed but never really used (I simply replaced the pot as it had a bent shaft). This piece of equipment was ripe for repurposing. After a little research, I determined what the ME-6B expected from its expression pedal: using a stereo 1/4" cable, the tip is connected to the middle pin of the pot, while the ring and sleeve are connected to the other two pins. Also: since it's a digital effects board, the pot should have a linear taper. An analog taper works but, obviously, the volume curve is pretty horrible. Finally, I used a 100Kohm pot but I suspect any resistance value would work fine.
After opening the volume pedal, I removed the existing pot (100Kohm, analog) and both mono 1/4" jacks. I then installed a 100Kohm, linear taper pot I had lying around (the shaft, while shorter than the original, proved to be just long enough) and wired it to a single stereo 1/4" jack (as described above). A fairly simple procedure and, after plugging it into the effects board, I confirmed that it worked fine. Better than fine, actually: it worked perfectly.