HP-X Harmonic Percolator

Even-Order Harmonics

Introducing the HP-X a versatile distortion pedal inspired by the harmonic percolator.

Versatile Rock Machine

Whether you are searching for a harmonic-rich low gain overdrive distortion or a pedal that can achieve blown out gated fuzz tones, the HP-X is a solid choice for all types of rock music.

The pedal captures the signature even-order overdrive of the original harmonic percolator without compromising stability or volume and has variable input impedance so it sounds great anywhere in your signal chain. 

Watch this demo to hear its wide range of tones:

Great for Guitar and Bass

The HP-X retains plenty of low-end yet remains punchy with clarity in the high midrange, so it is a great choice for bass distortion.

On guitar, the pedal doesn’t get muddy when switching to the neck pickup.

Hear it on Bass in this demo:

Virtual Pedal Modeler

Try out the HP-X via this virtual pedal modeler from Loopy Demos. Swipe left/right under the play button for more settings.


HARMONICS: The input level – turning the knob to the right increases the compression, distortion and overall gating of the pedal going from nice even-order overdrive to gated fuzz.

Adjust this knob to change impedance level to work with with the pedal that comes before it in the chain.

BALANCE: The output volume.

CLIPPING: There are 3 clipping options:

Left: Asymmetrical Germanium Diode Clipping

Center: Diode lift for all transistor distortion

Right: Symmetrical Silicon Diode Clipping

What is a Harmonic Percolator?

A distortion pedal with fuzzy characteristics, the harmonic percolator circuit pairs a PNP and NPN transistor in a unique way to emphasize even-order harmonics and amplify your signal to destructive levels.

The Interfax Harmonic Percolator called the HP-1 was the first harmonic percolator.

Championed and made infamous by Steve Albini, the percolator is most commonly associated with varieties of abrasive rock music.

Many pedal builders have built their versions of this circuit and the HP-X continues that tradition.