The Nano Bass Big Muff Pi Distortion/Sustain Pedal from Electro-Harmonix is a harmonic distortion/sustain device for the electric bass guitar. The pedal is based on the Russian battle-tank green Sovtek Big Muff Pi from the late '90s, and the original Electro-Harmonix Big Muff Pi from the early '70s. You can use the unit to thicken up your sound, or give it a low-end growl. The unit runs on the included 9V battery, or on an optional US9.6DC-200BI power supply.