The Xotic AC Booster a well loved booster/overdrive pedal, this demo shows why –
And here’s a scheme for you:
You can clearly see it is a traditional style opamp based clipper. With one interesting addtion, it has an active tone stack present after the clipping section! Here’s some more info, available on the Xotic site: http://www.xotic.us/effects/ac_booster/
Kusi of the freestompboxes.org forum contributed these mods to change the xotic AC booster into the xotic RC Booster:
C1 = 47nF
C2 = 1uF / NP
R8 = remove and bridge
C4 = remove
R5 = 22k
R7 = 250k
Clipping-Diodes = 3x 1N4148 each side