The ZVEX Mastotron is a fuzz pedal from ZVEX, described by the maker as "a sub-heavy silicon fuzz with some new twists"1. Premier Guitar called it "Z.Vex's powerful and rowdy silicon fuzz generator"2. It sits in the maker's fuzz line alongside circuits like the Fuzz Factory and Woolly Mammoth, and it is aimed at players who want a tight, low-end-heavy fuzz rather than a vintage-style one.
The controls
The Mastotron carries six controls: Volume, Subs, PW (Pulse Width), Fuzz, and Relax/Push, plus a treble tone control12.
| Control | What it does |
|---|---|
| Volume | Output level2 |
| Fuzz | Fuzz amount2 |
| Subs | Three-position sub control switch1 |
| PW (Pulse Width) | Adjustable pulse width1; smoothly changes the waveform from a full square wave (left) to narrow pulses (right)2 |
| Relax/Push | Input impedance control, adjusts from passive pickups to line level1 |
| Treble tone | Tone control1 |
The Subs switch is the pedal's signature feature. Premier Guitar's reviewer wrote: "The three-way Subs control runs the gamut from huge, window-rattling low-end to a thin, reedy chirp."2
"The three-way Subs control runs the gamut from huge, window-rattling low-end to a thin, reedy chirp."
The Relax/Push control is worth a note for players with unusual guitars. ZVEX describes it as "an input impedance control (push/relax) that adjusts from passive pickups to line level"1. Premier Guitar explains the direction: turning it left lowers the impedance, which ZVEX says "softens" the input for active pickups, while passive pickup users are encouraged to max it to the right2.
If you use passive pickups, set Relax/Push fully clockwise; the lower-impedance settings are intended for active pickups or line-level sources2.
What reviewers said
Premier Guitar's review frames the Mastotron as a fuzz for players who want control and tightness over subtlety, saying "an inexpensive, tight fuzz with signature tone and lots of control is the name of the game"2. The same review suggests bass players looking for a big fuzz tone should give it a whirl, while players after a more subtle, classic fuzz tone should skip it2.
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Questions
How much does the ZVEX Mastotron cost?
ZVEX Effects lists the Mastotron at $179.00 USD on its product page as of October 2026. Premier Guitar's review gave an MSRP of $149.99, so the price has moved over time. Check the maker's page for the current figure.
What does the sub switch do on the Mastotron?
The Mastotron has a three-position sub control switch. Premier Guitar's reviewer described the Subs control as running the gamut from huge, window-rattling low-end to a thin, reedy chirp, so it shapes how much sub-bass weight the fuzz carries.
What does the push/relax input impedance control do?
The Relax/Push control adjusts the pedal's input impedance from passive pickups to line level. Turned left it lowers the impedance, which ZVEX says softens the input for active pickups. Passive pickup users are encouraged to max it to the right.
How big is the ZVEX Mastotron?
ZVEX gives the pedal dimensions as 4.70 x 2.38 x 1.82 inches (LxWxH).
Where can I download the Mastotron manual?
ZVEX links a PDF of the instructions directly from the Mastotron product page at zvex.com.
Sources (2)
- Mastotron, ZVEX Effects
- Z.Vex Distortron & Mastotron Pedal Review, Premier Guitar, 2009-06-22
