The BearFoot Pale Green Compressor is an exact replica of the BJFe Pale Green Compressor ... already famous for its nearly transparent compression and dead quiet operation. You will want to leave it on all the time. You will also wonder if its on at all ~ until you turn it off to make sure and then turn it back on as quickly as possible. The middle knob fine tunes the EQ. Voltage range 8~18v.