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Function f(x) Clusterfuzz Review

Ferocious fuzz with remarkable range.

Clusterfuzz from Function f(x) takes an old idea and teaches it new tricks. At its heart, the pedal is a retro-style fuzz with two silicon transistors, in the vein of the Jordan Bosstone, Mosrite Fuzzrite, and post-germanium Fuzz Faces. But here, a clever set of extra controls greatly extends the tonal range of that classic combination.

Fuzz on Fire
Clusterfuzz feels and looks solid. Its pots are board-mounted, but its jacks are not, decreasing the chance of long-term damage. The footswitch is a soft-touch relay. The pedal runs on battery power or via a standard power supply (not included).

The core Clusterfuzz sound is loud and nasty, thanks to its MPSA13 and 2N5089 transistors—two ultra-high-gain components that collectively generate tsunamis of sizzling fuzz. But that core sound is a just a starting point.

Unlike some ’60s predecessors, Clusterfuzz includes a truly versatile tone control. Two, actually—there’s a treble-cutting tone pot at the end of the circuit, plus a filter toggle that nixes highs upstream from the transistors. The former rounds the edges of those sharp, ultra-high-gain tones, while the latter trims top end from the signal feeding the transistors, taming their response. The two controls yield distinctive results, and combining them unlocks many useful shadings.

But while these controls capably soften the pedal’s explosive highs, Clusterfuzz isn’t really about smooth/warm/pretty distortion. Even with maximum treble-cut, tones lunge at your ears with fangs bared and claws extended.

As on a silicon Fuzz Face, tones clean up nicely when you lower your guitar’s volume. (Lowered-volume tones aren’t quite indistinguishable from effect-bypassed ones, though they’re close.) In-between settings provide useful variations, though high-gain fuzz comes on early and strong. Clusterfuzz really wants to scream.


Super-loud. Super-aggressive. Great tonal range.

Not for the faint-hearted.


Ease of Use:




Function f(x) Clusterfuzz

Diodes for Days
Dual-transistor fuzzes can sound great with clipping diodes (Bosstone-style) or without (Fuzz Face-style). Clusterfuzz doesn’t merely offer both options—a five-way switch selects from four different diode combinations, plus a no-diode setting. The distinctions aren’t subtle—flicking the switch dramatically alters the circuit’s timbre.

Clipping diodes always cut level, so the no-diode option is by far the loudest. It’s a full-frequency roar with walloping lows and enough gain to pummel any preamp. The diode settings are quieter, more compressed, and filtered in varying ways. (Though trust me—you won’t find the Clusterfuzz short on power at any setting). The LED clippers reign in lows and add a touch more distortion. The FET option pairs a 2N7000 MOSFET with a silicon diode for a slightly less edgy sound. The S1 setting uses a pair of conventional silicon diodes for a more compressed sound, while S2 adds a Schottky diode to the mix for even greater compression and sustain. Executive summary: tons of tones.

A Bit Less
But wait—Clusterfuzz has one more trick up its sleeve: an “8-Bit” control. No, it’s not really digital bit reduction—just a pot that increases gain going into the second transistor. At high settings, the transistor farts out, yielding a variety of broken/sick fuzz tones. It ain’t pretty, but it’s cool.

All these controls are intensely interactive—with each other, with the pedal’s fuzz (gain) knob, and your guitar level. (If you switch from a guitar with vintage-style pickups to one with high-gain pickups, you’ll damn well hear the difference!) You can spin endless variations on the core sound, though at almost all settings, Clusterfuzz remains uncompromisingly aggressive.

The Verdict

Clusterfuzz isn’t some one-trick pony. It’s a magic circus pony! Mind you, it’s no petting-zoo animal—it’s a vicious beast eager to chew your face off. It boasts remarkable tonal range, though its focus is unvarnished aggression. The players likeliest to dig Clusterfuzz are ones who regard adjectives like “brutal” and “sick” as lofty compliments.

Watch the Review Demo: