Electro-Harmonix Metal Muff Distortion with Top Boost Guitar Effects Pedal High input impedance buffered bypass Output volume and master drive controls 3-Band EQ: bass, mid and treble Foot switchable Top Boost with separate control knob 9-volt battery included, Optional 96DC-200BI power supply available Knob controls include Distortion, Bass, Midrange, Treble, Top Boost and Output volume. The unique Top Boost knob allows you to dial in frequencies that center between 3.5 kHz & 4.3 kHz Buffered Bypass