Fairfield Circuitry 20% More

The Fairfield Circuitry 20% More is a distortion pedal with an unusual engine: instead of the clipping stages found in most distortion circuits, it applies a slew limiter, a circuit normally found in modular synthesizers, to shape guitar and other audio signals¹. The result, as the Quebec-based maker describes it, is a "Slew Limiting Distortion" that behaves less like a conventional overdrive and more like a filter that distorts as it works².

Fairfield Circuitry, a Quebec-based pedal maker with a reputation for unconventional designs³, positions the 20% More alongside pedals like the Roger That RF-inspired distortion: a different style of distortion rather than another take on a familiar sound⁴. Note that the pedal is currently listed as sold out on the maker's own product page².

What a slew limiter does to guitar

A conventional distortion pedal clips: it chops off the peaks of the waveform to add harmonics. The 20% More takes another route. As Fairfield Circuitry explains on its product page:

In practical terms, the circuit caps how fast the signal's voltage can rise or fall. Fast-moving content, which corresponds to high frequencies, gets rounded off, while slower content passes through. The maker says that when the circuit resonates, those fixed slopes become triangle wave oscillations, which is what gives the pedal its particular character².

Guitar Pedal X's Stefan Karlsson described the outcome as "a sort of Distorted Low Pass Filter, with elements of wave folding," and noted it delivers "a cool somewhat clangy distortion voicing"⁴. Delicious Audio's Paolo De Gregorio framed the same idea from the synth side: at the pedal's core is a slew limiter, "a circuit typically used in modular synths to shape control voltages"⁵.

The pedal also includes a CV input for the slew limiter frequency⁴, which opens the door to controlling the filter cutoff from outside the pedal, the way a modular player would.

The controls

The control set mixes standard distortion controls with the slew limiter's own parameters. Guitar Pedal X lists the full layout⁴:

The octave up switch is worth a closer look. Delicious Audio explains that it "activates a full-wave rectifier circuit, which produces an upper-octave effect by doubling the frequency of the input signal, adding grit and harmonic complexity"⁵. That puts it in the territory of octave and pitch pedals, but as a switchable color on the distortion rather than a dedicated octave effect.

The envelope follower is the other distinctive element. As De Gregorio describes it, it "dynamically adjusts either the Feed amount or the output's low-pass gate (LPG) based on playing intensity"⁵. The Envelope knob selects which of the two it tracks, so playing harder can either push the feedback or open and close the low-pass gate, giving the pedal a touch-responsive, almost filter-like behavior.

Where the circuit came from

The origin story is unusual even by Fairfield Circuitry's standards. The maker's product page describes the project as²⁴:

Guitar Pedal X tells the same story: the project started as a study of a mysterious old schematic that looked like a datasheet square/triangle oscillator, and what Fairfield Circuitry ended up with was the distorted low-pass-filter distortion the pedal became⁴. The maker's note that the fixed slopes become triangle wave oscillations when the circuit resonates² connects directly to that square/triangle oscillator heritage.

Price and availability

The pedal entered wide international distribution in April 2025, when Guitar Pedal X reported it at S$389 CAD (about $270 USD at the time) on the Fairfield Circuitry webstore⁴. Delicious Audio covered it as the maker's latest offering in September 2025⁵. As of October 2026, the maker's own page lists it at a regular price of $455 CAD and shows it sold out².

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