Bass Overdrive/Pre-Amp - Two channel bass effect consisting of a pre-amp and an overdrive which may be used independently or combined. Specially designed circuit lets original bass tone to pass through without affecting the low end. Controls include a pre-gain control for up to 5db boost, overdrive gain, tone and level controls, and an EQ shift switch for a warmer smoother tone when engaged. True hardwire bypass. Operates on battery or negative center DC power supply (not included).