The Function f(x) Accufunkture is an envelope-controlled filter effect, also known as an auto-wah or envelope filter. It listens to the dynamics of your playing and sweeps a filter in response to your pick attack, producing the touch-controlled wah sound pioneered by the original envelope follower, the Mu-Tron III.12
Circuit heritage: the Mu-Tron Micro V
Function f(x) is explicit about where the design comes from. The manual states: "We started with the classic Mutron Micro V circuit (which is the little brother to the old Mutron III filter)."3
The Mu-Tron Micro V was Mu-Tron's own envelope-controlled filter device, described by the maker as "an advanced envelope-controlled filter device" carrying on "the touch-controlled wah effect pioneered by the original envelope follower, Mu-tron III."4 As an independent circuit analysis puts it, the Micro V delivered "a similar effect to the Mu-tron III, but with a completely different circuit topology," making it the lower-cost alternative in the original Mu-Tron line.5 The Mu-Tron III itself worked as a voltage-controlled filter whose peak response frequency was "varied in accordance with the varying envelope of the sound generating signal," which is the principle any envelope filter, including the Accufunkture, follows.6
"We also modernized the parts selection so that only current-production parts are used, thus eliminating the problem of parts scarcity."
That modernization matters for a player: the original Mu-Tron designs relied on parts that have become scarce, while the Accufunkture keeps costs down by using only parts still in production.3
Controls and how it works
The manual documents the Sense control, short for Sensitivity: it "controls the intensity of the envelope dynamics generated by the pick attack. Higher settings provide greater drive of the intensity of the swept filter." In practice, Sense sets how hard the filter reacts to your playing, from subtle sweeps on a light touch to wide-open auto-wah on aggressive picking.3
Power, size and switching
The Accufunkture runs on 9V DC, which Function f(x) calls the industry standard, through a 2.1mm center-negative barrel connector. It draws 20mA when engaged and 10mA when bypassed.23 As a full-size Function f(x) pedal, it uses "a soft-touch, relay-based true bypass switching system," so your signal passes through a relay rather than a conventional footswitch when the pedal is on.12
| Specification | Value |
|---|---|
| Enclosure size | 4.78 x 2.61 x 1.6 in (12.14 x 6.63 x 4.05 cm) |
| Weight | 10 oz (283 g) |
| Power | 9V DC, 2.1mm barrel, center negative |
| Current draw | 20mA engaged, 10mA bypassed |
| Bypass | Soft-touch, relay-based true bypass |
| List price | $189.00 USD (2026-09-02) |
The Accufunkture's list price on the maker's product page was $189.00 USD as of 2026-09-02.2
Warranty and service
Function f(x) covers the Accufunkture against defective parts and workmanship for 1 year from the date of purchase, excluding damage caused by user error. After the warranty period, repairs may incur a fee to cover parts and labor, with no costs paid upfront. If a full PCB replacement is needed, the company advises it may take as long as 4 to 6 weeks if critical parts are unavailable.3
Videos
Mike Hermans
David DeMaria
Questions
What circuit is the Function f(x) Accufunkture based on?
Function f(x) started with the classic Mu-Tron Micro V circuit, which the company describes as the little brother to the old Mu-Tron III filter. The Micro V was Mu-Tron's lower-cost envelope filter, with a different circuit topology from the Mu-Tron III but a similar touch-controlled filter effect. The Accufunkture modernized the parts selection so that only current-production parts are used.
How much current does the Accufunkture draw?
The Accufunkture draws 20mA when engaged and 10mA when bypassed, running on 9V DC, which Function f(x) calls the industry standard. It uses a 2.1mm barrel connector with center-negative polarity.
Is the Accufunkture true bypass?
Yes. As with all Function f(x) full-size pedals, the Accufunkture features a soft-touch, relay-based true bypass switching system.
How long is the Accufunkture warranty?
Function f(x) warrants its pedals against defective parts and workmanship for 1 year from the date of purchase. The warranty does not cover damage caused by user error. Repairs after the warranty period may incur a fee for parts and labor, and no costs are paid upfront.
How big is the Accufunkture pedal?
The enclosure measures 4.78 x 2.61 x 1.6 inches (12.14 x 6.63 x 4.05 cm) and the pedal weighs 10 oz (283 g).
Sources (6)
- Accufunkture Envelope Filter / Auto-Wah, Function f(x), 2017-06-13
- Accufunkture Envelope Filter, Function f(x), 2026-09-02
- Parallax Tremolo + Phaser, Function f(x), 2020
- Mu-Tron Micro V, mu-tron.com
- Minima Resonant Filter / Mu-tron® Micro V, Aion FX, 2023-09-08
- Guitar FX Layouts: Mutron III, Guitar FX Layouts (tagboardeffects.blogspot.com), 2014-06-19
