The Electro-Harmonix Percolator is a fuzz pedal based on the 1970s Harmonic Percolator, a circuit Electro-Harmonix itself describes as a "Harmonic Saturator"1. Announced in June 2026, it is a budget take on the Interfax HP-1 Harmonic Percolator, the rare, gooped, cult-status fuzz that came out of a Milwaukee repair shop in the 1970s231. Where an original HP-1 offered only two sliders, the EHX version adds a Bias control and a Drive/Fuzz gain-range toggle, giving the player more ways into the circuit's distinctive distortion without cleaning up its personality23.
A take on the Interfax Harmonic Percolator
The original Interfax HP-1 Harmonic Percolator was built with germanium transistors and, unlike most germanium fuzzes, uses clipping diodes6. It carried two controls: Balance and a "Harmonics" input-gain slider7. Originals are rare, gooped (their circuitry hidden under epoxy), and carry a cult status that has spawned a whole family of clones and variants, from Fredric Effects' part-for-part Silicon Harmonic Percolator to the Emerald Ox FX Chimeric Percolator38.
The EHX Percolator is Electro-Harmonix's entry in that lineage: a budget take on the HP-1 with two extra controls, aimed at making the HP-1 "a little more accessible," as Premier Guitar put it25. Delicious Audio called the underlying circuit "a re-elaboration of a circuit so legendary that most of its history is still guesswork"3.
Premier Guitar's reviewer found the pedal holds on to what makes the original special5:
"The EHX Percolator captures these fundamental, and sometimes alchemical, aspects of the HP-1's voice5."
Premier Guitar, September 20265
The controls: Harmonics, Bias, Balance and the Drive/Fuzz toggle
The front panel carries three knobs and a toggle. Two of the knobs correspond to the original HP-1's pair: Premier Guitar describes them as "effectively a master volume and an input gain control (which functions more or less like a guitar volume knob)"5. The Bias knob and the Drive/Fuzz toggle are the additions.
| Control | What it does |
|---|---|
| Harmonics | Controls the gain at the input; turning it clockwise makes the signal more saturated and distorted1. Delicious Audio: "from mild overdrive to full destruction"3 |
| Balance | Sets the output level13 |
| Bias | Adjusts the gain circuit's bias; Delicious Audio says it ranges from smooth drive to pseudo-octave effects to gated, sputtering Velcro fuzz3 |
| Drive/Fuzz toggle | Engages or lifts the clipping diodes13 |
The Bias control is the addition Premier Guitar's reviewer singled out, noting it "alters the distinctive distortion flavor in ways an original HP-1 cannot, and in a manner that a tone or gain control never would"5.
Drive versus Fuzz mode
The toggle switches the clipping diodes in or out of the circuit13:
- Fuzz mode: the clipping diodes are engaged for heavy, compressed fuzz; Delicious Audio says "the diodes clamp down and it gets nasty"34
- Drive mode: the clipping diodes are disengaged and the pedal acts more like a transistor overdrive and distortion, "raw, chewy, crunchy" in Delicious Audio's words13
Premier Guitar's reviewer found the drive mode often sounds closer to the HP-1's voice than the fuzz side, and argued the hard clipping "has a flattening effect that strips away the drive mode's most alluring complexities"5.
Footswitch and internal trim pot
The footswitch includes a momentary action: pressing and holding it for more than half a second returns the pedal to its previous state when you release it, so you can hold for a burst of fuzz and let go1. The momentary action may be disabled if you want a standard latching switch1. Inside the enclosure there is an internal trim pot for sub-octave enhancement and extra gain3.
The pedal runs on 9V center negative3, the common pedalboard standard, so it fits a typical 9V power supply chain.
From a Milwaukee repair shop to Electro-Harmonix
The Harmonic Percolator was designed by electrical engineer Ed Giese at his Milwaukee, Wisconsin audio repair shop, Interfax, in the 1970s486. The original HP-1 came with germanium transistors6, and its simple but fascinating circuit has long lent itself to tweaking and improvement, which is why so many builders have made their own versions910.
Electro-Harmonix announced its version on June 17, 2026, described by Gearnews as "a new $99 version" of the Interfax Harmonic Percolator circuit with a different user interface4. Guitar Pedal X introduced it the next day as a budget take on the HP-1 with two extra controls, available in the USA for $992. The enclosure leans into the original's homemade look, with faux printed-on Dymo-style labels designed to look out of alignment2.
Price and availability
Published prices disagree. At announcement, Gearnews and Guitar Pedal X both gave the US price as $99, with Gearnews also listing $96/£86/€9924. Delicious Audio's July 2026 write-up listed it at $1293, and Premier Guitar's September 2026 review still called it "for $99, a crazy-inexpensive and super-cool way to extract yourself from a distortion tone rut"5. Gearnews reported it available to order at Thomann with a two to three month wait at launch4.
What reviewers said
Premier Guitar's September 2026 review is the fullest published assessment. Its verdict: the pedal captures the HP-1's fundamental voice, the bias control adds something a tone or gain knob never could, and the drive mode often lands closer to the original than the fuzz mode, though the reviewer felt the fuzz mode's hard clipping flattens the drive mode's complexities5. Delicious Audio summed the pedal up as "just a weird, angry circuit that sounds like nothing else on the shelf"3.
Videos
EHX
Eirik Stordrange
Rich. Words. Music.
Questions
Is the EHX Percolator true bypass?
Yes. Electro-Harmonix says the pedal employs true bypass with a mechanical relay, so the signal passes around the circuit when the pedal is off. Delicious Audio's write-up also lists it as true bypass.
Does the Percolator have a momentary footswitch?
Yes. The footswitch works in latching or momentary action: pressing and holding it for more than half a second returns the pedal to its previous state when you release, giving a burst of fuzz on demand. Electro-Harmonix notes the momentary action may be disabled if you prefer standard latching operation.
What does the internal trim pot on the Percolator do?
Inside the pedal there is an internal trim pot for sub-octave enhancement and extra gain, according to Delicious Audio. It is not a front-panel control, so getting at it means opening the enclosure.
How much does the Electro-Harmonix Percolator cost?
At launch in June 2026 it was announced at $99 in the USA, and Premier Guitar's September 2026 review still called it a $99 pedal. Delicious Audio listed it at $129 in July 2026, so the published prices disagree.
What is the difference between Drive and Fuzz mode on the Percolator?
The toggle engages or lifts the clipping diodes. In Fuzz mode the diodes are engaged for heavy, compressed fuzz; in Drive mode they are disengaged and the pedal behaves more like a transistor overdrive and distortion. Premier Guitar's reviewer found the drive mode often sounds closer to the original HP-1's voice.
Sources (10)
- EHX Percolator, Electro-Harmonix (ehx.com)
- Guitar Pedal X, Guitar Pedal X, 2026-06-18
- Electro-Harmonix Percolator, Delicious Audio, 2026-07-02
- EHX Percolator: Based on '70s Harmonic Percolator, gearnews.com, 2026-06-17
- Electro-Harmonix EHX Percolator Review, Premier Guitar, 2026-09-19
- Particle Vintage Fuzz / Interfax Harmonic Percolator, Aion FX, 2021-02-19
- Guitar Pedal X, Guitar Pedal X, 2024-05-13
- Paperboy Pedals Harmonic Percolator Clone, Pedal of the Day, 2024-02-08
- Guitar Pedal X, Guitar Pedal X, 2025-07-21
- Fredric Effects Releases the Utility Perkolator, Premier Guitar, 2014-09-09
