The Electro-Harmonix XO Big Muff Pi is a distortion pedal that gives bass players the well-loved distortion the original Big Muff is known for with no loss of low end. This Bass Big Muff Pi pedal features controls for volume, tone, sustain, dual outputs (effect and dry for recording), and a mini switch for bass boost. The Electro-Harmonix Bass Big Muff Pi distortion pedal is powered by a single 9-volt battery or optional AC power supply (sold separately).