Updated Feb. 3, 2022

The BSRI Audio Hydrazine is a modern take on the Harmonic Percolator fuzz circuit by an emerging Baltimore-based builder (BSRI stands for Baltimore Sonic Research Institute, but it’s actually a one-person company).

The Hydrazine employs NOS germanium and silicon transistors and germanium diodes found in the vintage unit, but through tailored mods improves clarity and punch, providing the player with a sider range of sonic possibilities.

The Tone, knob, not present in the original, delivers basic tone sculpting, while the Texture knob allows to vary the clipping threshold, producing a wide range of tones “between transistor overdrive and compressed full diode clipping distortion.”

Here’s the first video of the BSRI Audio Hydrazine fuzz. We added it to our article about the best Harmonic Percolator clones and evolutions.

BSRI Audio Hydrazine Fuzz, Builder’s Notes

Hydrazine is a modern interpretation of the Interfax Harmonic Percolator with updates to give players a wider range of tones and textures. The core amplifier circuit has been modified for improved clarity and punch with period-correct NOS germanium and silicon transistors and germanium diodes. The active tone stack provides ample range in the bass and treble frequencies for shaping the distorted tone to meet the needs of both guitar and bass players. Finally, a unique Texture controls allows for continuous adjustment of the clipping threshold for a wide range of tones between transistor overdrive and compressed full diode clipping distortion.