Univox Square Wave Fuzz

The Univox Square Wave Fuzz is a vintage fuzz pedal built around square-wave clipping, sold under the Univox name and associated with Shin Ei. Its best-documented player is Kurt Cobain, who used it during the In Utero sessions¹. It belongs to the wider family of fuzz pedals, a category where Univox also made its mark with the Super Fuzz.

What it does

The pedal's single gain control was called "Distortion" in the original¹. One characteristic worth knowing before chasing one down: according to Guitar Pedal X, the original "barely reached unity at max level," meaning even with the level control full up the pedal could struggle to be louder than the clean signal feeding it¹. That is a real limitation on a pedalboard, and it is the main thing modern versions set out to fix.

Modern versions of the circuit

The Square Wave Fuzz circuit has been picked up by two current builders²¹:

• Fredric Effects Square Wave Fuzz: described by its maker as "a new version of the classic Univox/Shin Ei Square Wave Fuzz"².
• Drunk Beaver Bucha Square Wave: based on the Univox Square Wave Fuzz, with builder Vitalii Bobrov adding "a real gain control (Fuzz) and additional gain recovery stage after the tone stack" to address the original's low output¹.

Both versions keep the original's square-wave character while, in the Drunk Beaver case at least, adding the gain recovery the vintage unit lacked¹.

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