Does anyone know how to build a fixed expression pedal version of a Moog EP-3? My brother has an MF Boost that he uses for bass, and we wanna build a little Hammond 1590A size footswitch that will work as a switchable preset boost for that pedal (expression pedal controls the gain knob). I know we'll need a TRS jack, a switch, and a pot, but I'm not sure what value potentiometer or how to wire it up, or if we can wire an LED to light up when activated (powered from the pedal if possible). Can someone help with a diagram? Thanks!