I’ve been in a few metal bands in my younger years playing Guitar and Bass. I’ve tried all kinds of effect stomp boxes and amps with my guitars. I even made a few or modified a few effect pedals. A friend of mine that also plays guitar asked me since I am keen with electronics if I could develop a volume pedal that works like a “wah-wah” pedal. However just not no typical volume pedal at that. The specs he requested are pretty neat and I even upped the ante by added a third jack for mixer/tuner output and a preamp booster.
The circuit is a simple LPB-1 Booster from Electro Harmonix. Instead of a stomp box configuration it will be housed in a wah-wah/expression pedal configuration. Already I had to make some modifications to the circuit itself. Instead of a 2n5088 like all of the schematics I have found call for I used a more modern audio TO3p style transistor and also changed out the caps from 100nF to 150nF because there was a bad hum. To power the circuit a LM7805 regulator is needed since most likely a wall-wart will be used. It will cut the hum from the 60Hz AC mains voltage from creeping in. From my testing 5 volts works just fine and also helps add another function to the pedal. One of the requests was a LCD display to show what the volume level is. To achieve this a 2X taper potentiometer is needed because a Arduino will be used to control the LCD. Basically the second side of the pot will control some analog pins on the Arduino and then put the output onto a small 16×2 char LCD. Granted I could make the whole thing digital but most guitar/bass players including myself prefer analog, it sounds more raw then studio mix up crap like Dragon Force.
When the whole project is done I’ll toss up some pictures.