I call it the Zimmerman Thunder Boost. It uses a J201 JFET Transistor to give your signal a tube like boost. The knobs control your signal going into the JFET and Volume out to the rest of your rig to ensure you are getting the signal tone and output you want. The simple toggle switch lets you go from simple boost - lighting treble boost - or thundercloud gain boost. This pedal can utilize a 9V, 12V, or 18V power supply.