Using a 12AX7 tube, and powered from an external 15VAC to 16VAC supply with a 2.1mm plug, this pedal runs the tube in starved plate mode, for that real tube sound. Many pedals on the market have the word "tube" in their name, and while these can be quite good, they don't use a real tube to get "that sound". This is the Mozztronics take on a pedal with an actual 12AX7 tube inside. Some products with tubes use the tube for filtering only, in the tone control section of the circuit. What a waste of a tube. We here at Mozztronics use the tube where it is meant to be used, in the gain stages, so the drive you hear is tube drive. GAIN controls the amount of overdrive from a light crunch to a searing screaming overdrive, TONE adjusts the brightness of the signal, VOLUME adjusts the overall output volume of the pedal, and there is a 3 position CONTOUR switch to select between mild / normal / heavy.