The MXR M104 Distortion+ is a classic guitar effects pedal known for its versatile, hard-clipped distortion tone, ranging from warm overdriven blues to thick, fuzzy 80s rock. It features two main controls: a Distortion knob and an Output knob, and can be powered by a 9-volt battery or an AC adapter. The pedal uses germanium diodes and a capacitor to create a warm, rounded sound that is never shrill.