The Electro-Harmonix Mole Bass Booster Pedal helps bassists and guitarists unearth a positively subterranean sound. Based on the classic design, this updated Electro-Harmonix pedal adds the same rich, low-end bottom while adding a 20dB boost to your signal. Whether you step on the Mole to get deep, ground-shaking drive or dial back the knob to add some texture to your existing tone, the Electro-Harmonix Mole Bass Booster digs wherever you tell it to.True Bypass Up to 20dB of LOW frequency gain to any amp Center frequency of 400 Hz to 200 Hz at maximum volume Tough and compact die-cast chassis 9-volt battery included 96DC-200BI power supply