Electro-Harmonix Nano Bass Big Muff Bass Distortion Effects Pedal Tailor your drive/distortion sound with Sustain, Tone and Volume knobs Features a Dry switch that mixes your dry bass, at unity level, with the Nano Bass Big Muff's distortion True bypass for maximum signal path integrity Road worthy die-cast chassis 9 Volt battery included. Optional EHX 9.6DC-200 AC adaptor available