Function f(x) Clusterfuzz

The Function f(x) Clusterfuzz is a fuzz pedal built by Function f(x) LLC, launched in January 2015 as the company's first product¹. Function f(x) describes it as a new design using modern components for consistent performance and a long operational life, and states plainly that it is not patterned after any existing classic or modern boutique fuzz pedal²¹. In the maker's own words from the manual, "It can go from a medium gain overdrive to a broken-sounding square wave fuzz machine."³

What sets it apart from most fuzz boxes is the combination of five selectable clipping modes and a dedicated 8-Bit knob that dials in gated, square-wave fuzz sounds². Premier Guitar's review placed its character "in the vein of the Jordan Bosstone, Mosrite Fuzzrite, and post-germanium Fuzz Faces," while crediting its aggression to its MPSA13 and 2N5089 transistors, two ultra-high-gain components⁴.

The controls

The front panel carries three knobs, Volume, Tone, and Fuzz, plus the 8-Bit knob and a five-position clipping selector². The manual explains what each does:

The 8-Bit control is the unusual one, and the manual explains how it works: "The 8-bit control basically lets the signal from the first transistor in circuit to drive the second transistor harder." Past a certain level the second transistor distorts massively, producing a square-wave output³. Pedal of the Day's reviewer called it "an 8-bit knob lets you dial in some incredible gated fuzz sounds, adding a new and unexpected element to any 'normal' fuzz you might be used to."⁵

The manual also suggests starting points for different sounds:

• Overdrive-ish: keep 8-Bit low; the FET clipping setting gives a good balance of dynamics, smoothness, and clarity³
• Compressed metal fuzz: crank the Fuzz, move 8-Bit to taste, try Si1 or Si2; for maximum compression and sustain choose Si2³
• Broken fuzz: keep the 8-Bit up; it is more audible in lower compression settings such as LED clipping³

The footswitch is a soft-touch relay, as noted in Premier Guitar's review⁴, and the maker lists the bypass as soft touch (true) bypass².

Five clipping modes

The Mode knob selects among five clipping configurations, which the manual describes setting by setting⁵²:

The progression runs from wide open to heavily compressed, so a player can move from a loud, dynamic fuzz to a tight, sustaining one without touching another control. Pedal of the Day listed the same five options in its 2016 review⁵.

Power, buffers, and warranty

The Clusterfuzz runs on 9V DC, and the manual is specific about the supply: "Make sure that you use a 9VDC center negative 2.1mm barrel power supply to power the Clusterfuzz."³ Current draw is 20mA engaged and 10mA bypassed². Premier Guitar's review also notes the pedal runs on battery power or via a standard power supply, which is not included⁴.

Function f(x) warrants its pedals against defective parts and workmanship for 1 year from the date of purchase, not covering damage from user error. After that period, repairs may incur a fee for parts and/or labor, with no costs paid upfront, and a full PCB replacement may take as long as 4 to 6 weeks if critical parts need to be ordered³.

Where it came from

Function f(x) LLC announced the Clusterfuzz on January 19, 2015, as its first product, describing it as a gain pedal with five clipping levels, an input low-pass filter, and in-house relay-based bypass¹. The enclosure features laser-etched artwork². The design uses modern components chosen for consistent performance and long operational life¹.

What reviewers said

Premier Guitar reviewed the pedal in August 2021 at a street price of $199⁴. The reviewer's summary of strengths was short and direct:

Pedal of the Day reviewed it in April 2016, highlighting the 8-Bit knob's gated fuzz sounds as an unexpected element compared with a normal fuzz⁵. Guitar.com's reviewer, writing about the Function f(x) line in 2026, noted the Clusterfuzz "has a number of different clipping options and filters in a compact package."⁹

The Jr. and Micro versions

Function f(x) offers the same basic tones in two smaller footprints: the Clusterfuzz Jr. and the even-smaller Clusterfuzz Micro². Both use the same circuit under the hood, with fewer features to fit smaller enclosures, and the same types and values of components as the full-size pedal⁶¹⁰.

The Jr. was scaled down to a smaller footprint based on feedback from customers⁷, and its manual describes it as a more compact version of the original full-sized Clusterfuzz, capable of going from a medium gain overdrive to a broken-sounding square wave fuzz machine³. Its LED/SI switch selects between LED clipping (up), no diodes (center), and silicon diodes (down)⁸.

DIY layouts

Builders in the comments verified several parts substitutions: 680pF for C1, 1N5817 for D4 and 1N4001 for D3, and a current limiting resistor of 4k7 for the LED (2k2 or 1k for a brighter one)¹¹. For the LED clipping diodes, red LEDs with a forward voltage of 1.8 to 2v work, orange, yellow, or green are similar, and blue or white should be avoided; two or three 1N4148/1N914 pairs in series give a similar sound¹¹. One builder reported that the 1k resistor after the tone pot is missing from the layout schematic¹¹.

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