Op-amp Big Muff Pi

In the late 1970s, Electro-Harmonix experimented with op-amp-based Big Muff circuits. The IC chips replaced discrete transistors, changing the character significantly.

The op-amp version has more gain, more aggression, and a different clipping character. It's tighter and more focused than the transistor versions. Billy Corgan famously used this circuit on Smashing Pumpkins' Siamese Dream.

The original op-amp Big Muffs became rare and expensive. EHX released the reissue to make that specific sound accessible again.

The Big Muff variation that defined 90s alternative rock fuzz.