Harmonic Equalizer


Specifications and Operation

The HEQ1 'Harmonic Equalizer' is an instrument-level device capable of obliterating audio signals. There are two modes: Standard and Multiply. In both modes, there are two distinct methods employed to maximize audio irregularities.

The first method, labelled Harmonic Distortion, consists of cascaded common-emitter Darlington gain stages biased to produce specific wave-shaping characteristics. The resulting level of sonic disintegration varies with the settings of the two controls - Edges, and Expanse.

Edges controls envelope behavior, saturation levels, and gating effects.

Expanse controls harmonic complexity, treble response, and compression.

Due to the nature of the circuit, these controls are incredibly interactive and have different results depending on the settings in other sections.

The second stage, labelled Baxandall Equalizer is a three-band active tone control based on the published work of Peter Baxandall in 1952. All three bands are in the feedback path of an operational amplifier, allowing for optimized impedance balancing and make-up gain. These three bands are labelled BassMid, and Treble.

Bass is a shelving filter with 15dB of boost or cut at frequencies below 325Hz.

Mid is a wide-band peaking filter with 15dB of boost or cut centered around 1,500Hz.

Treble is a shelving filter with 15dB of boost or cut at frequencies above 7,250Hz.

As with the previous stage, all of the tone shaping controls interact with the other controls to form nearly limitless sonic possibilities. Do not assume that a particular knob position will do the same thing in all situations.

Volume controls the final output level of the device. With certain settings, it is possible to get significant gain when the volume is turned up, while other settings will require the volume to be set to maximum for unity gain.

In Standard mode, the HEQ1 can produce a myriad of fuzz tones, including modern gated fuzz sounds and complete signal breakdown. When Multiply is engaged, the level of havoc is increased exponentially. In this mode, the pedal is capable of producing much more volume, much more harmonic distortion, and in certain settings, bit-crusher-like effects.

Do not underestimate the power of the tone controls! Altering the frequency content of the distortion can fundamentally change the response of the device.


Sample Configurations

With all of the complexities inherent in this device, it is helpful to have a few sample configurations to start your journey. Keep in mind that the HEQ-1 is highly responsive to the pickups used and input level. Try experimenting with your guitar volume and pickup settings. The following configurations have been discovered by a tireless team of audio enthusiats.


San Fran Fuzz

In this mode, the HEQ-1 responds similarly to early fuzz circuits. Think of these as "San Francisco" tones (compare to early Santana, Grateful Dead, Jefferson Airplane, etc). 



Turning up Edges and Expanse a little more, while boosting the Mids and pulling out the Bass and Treble will move the tones into Black Flag territory. This is a raunchy fuzz tone.



Turning Expanse all the way down makes the Edges control have more of a "dead battery" effect. If you were to set your amplifier on fire, this is what it might sound like while it was melting. (Do not set your amplifier on fire)


Spirit in the Sky

Activating Multiply moves the circuit into higher gain territory. This setting sounds somewhat similar to the classic "Spirit in the Sky" fuzz tone. Try dialing back your guitar volume to get the right level of saturation.


Sick Angel

Turning up the Edges control in Multiply mode has a myriad of strange effects. With certain pickups, you may begin to notice a tremolo effect, or even a ring modulation effect. This is completely normal, don't panic.



Many people seek out the rich and explosive fuzz tones of vintage Russian Big Muff Pi pedals. In a side-by-side comparison, the HEQ-1 with these settings is considerably more rich and explosive. *Prone to feedback, beware.


Dark Arp

With these settings, it is possible to get the HEQ-1 to modulate the frequency rhythmically, resulting in an arpeggio-type response. Experiment with turning up the Edges control and/or changing the volume of your guitar.



If you find yourself without an instrument to plug into the HEQ-1, it is possible to use the device as an instrument itself. With these settings, it will produce a rhythmic clicking that can be altered by turning the knobs. This is especially effective when followed by a resonant filter and/or delay/reverb.