Catalinbread Perseus Sub-Octave Fuzz Guitar Effects Pedal Sub-octave fuzz so massive and thundering, youll regret turning it off Octave switch allows you to choose whether the sub-octave is one or two octaves down The Volume has plenty of output so you can pummel your amp to your heart's desire! Unity volume is around 10:00. The Blend allows you mix the fuzz and octave sounds in any amount you want. Full-counterclockwise will let you use just the fuzz sound. Full-clockwise will give you just the octave-down sound.