The ZVEX Vextron Series Mastotron is a five knob heavy silicon fuzz. The design includes a couple of unusual features: source impedance control, subs control, and pulse width control. It works equally well with bass and guitar, and can easily be interfaced with digital devices like recorders as well as keyboards.

Controls:

- RELAX/PUSH: This knob introduces source impedance to the signal going into the Mastotron. When fully up, the signal goes in raw... when turned down, source impedance is added as needed to "soften" the input for active pickups.
- FUZZ: This wide-range knob lets you set just how fuzzy your Mastotron gets.
- PW: Pulse Width control. You can swing this from square wave on the left to narrow pulses on the right.
- TONE: This shapes the treble without sacrificing the heavy subs.
- VOL: Output volume.
- SUBS Switch: "2-1-3" Lets you set how much sub content is in your fuzz. It's pretty dramatic -- 3 is huge, 2 is medium, and 1 has no bottom end whatsoever. Totally. Try 1 with the tone turned down.

The ZVEX Vextron Series Mastotron has very low current draw at around 1mA. It may be powered via 9 volt battery or a common 9 volt DC negative tip power supply.