“You could describe it as an early ‘boutique’ pedal company… but its products were made in a damp, rat-infested basement”: Loved by Nuno Bettencourt, Jeff Beck and Kurt Cobain, the ProCo Rat graduated from dank basements to the world’s biggest albums

ProCo Rat effects pedal on wooden floorboards.

Today’s guitarists are blessed with about 26,844 distortion pedals to choose from, give or take two. But back in the late ’70s the selection was much more limited, with stompboxes like the Electro-Harmonix Big Muff (which some would still call a fuzz unit), MXR Distortion+ and Boss DS-1 leading the way when it came to readily available products from big-name companies.

In 1978, a relatively small sound reinforcement company called ProCo Sound in Kalamazoo, Michigan, quietly introduced their own distinctive take of an op-amp-based distortion circuit combined with diode clipping and called it “The Rat.”