ZVEX Mastotron vs ZVEX Woolly Mammoth

Aug 19, 2026

Mastotron vs Woolly Mammoth is a fair fight between two ZVEX fuzzes that both hold onto low end where most fuzzes let it go. The Mammoth is the long-time bass classic; the Mastotron is the sleeper. The widget above plays both on the same bass loop, through the same chain and the same room, at the settings from my bass distortion shootout, so the comparison is like for like.

One honest note about the recording: the mild compression in the post-processing chain is bypassed for the Woolly Mammoth, because the two simply didn’t play well together. Everything else is identical.

ZVEX Mastotron

The Mastotron runs a silicon circuit voiced around a sub-heavy low end. Left to right the panel gives you Volume, a three-position Subs toggle for how much sub sits under the fuzz, Tone, Pulse Width marked PW, the Fuzz depth knob, and Relax/Push, which is an input impedance control running from passive pickup territory toward line level.

On bass it delivers extra oomph in the low end with a significant mid scoop, which makes it useful when there’s a busy guitar track to leave room for. It adds real body and weight while the sizzle up top is still enough to cut through.

What you’re hearing is worth understanding, because it doesn’t use the pedal’s gated side at all: PW sits at 0, which is the least starved the waveform gets, with Fuzz at 9 and Subs on position 1. Narrowing PW is how you make this circuit choke and gate, so at 0 you’re hearing the smoother, more amp-like end of its range rather than velcro. The full Mastotron demo sweeps PW across its full travel if you want to hear the other end.

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ZVEX Woolly Mammoth

The Mammoth was designed for bass first, built around a sub-frequency-preserving circuit meant to keep the lows that most fuzzes throw away. Four knobs: Output, EQ, Pinch and Wool.

Pinch is the signature. It squeezes the waveform’s pulse width, and as it climbs a gate starts choking the signal between notes, letting each one ring out before snapping shut. Wool sets how much furry saturation wraps around the note, or as ZVEX put it, the amount of fur. EQ moves smoothly between more bass and more treble rather than acting as a cut.

Here it runs Pinch at 6 with Wool right down at 2, so the gate is doing most of the work and the fur is pulled back. That’s the gated, grunty, almost synth-like side of the pedal rather than the thick woolly one, and on bass it turns a clean part into something with real teeth. The full Woolly Mammoth demo has sweeps for EQ, Pinch and Wool.

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Get This One If…

Get the Mastotron if you want weight and aggression without the gate getting in the way. The mid scoop makes space in a busy arrangement, the three-position Subs switch lets you decide how much bottom to add, and the Relax/Push impedance control makes it genuinely useful for reamping a bass or synth line. It’s the more predictable of the two, and the easier one to leave on for a whole section.

Get the Woolly Mammoth if you want the notes to choke. Pinch gives you a percussive, gated attack that suits riff-based playing where each note should close down cleanly instead of smearing into the next, and it’s the one that turns a clean bass into a grunty, synth-like monster. It’s a classic for doom, stoner and sludge for good reason, and it works on guitar just as well.