Stompbox Blog: ProCo Rat

Stompbox Blog

Welcome to the guitar effects virtual museum. I have been collecting stompboxes for the past few years and wanted to share some thoughts. I will continually add more pics and opinions. Any comments or suggestions are appreciated. Thanks for looking.

Tuesday, September 1, 2009

ProCo Rat

ProCo Sound Inc was founded in Kalamazoo, Michigan in 1970 with the moniker "striving for the utmost in clean audio gear". It's sad that they never fulfilled that promise however. Engineering director Scott Burnham was drawing up an over-the-top distortion unit when he noticed that he had an undervalued resistor in the drive stage because he had read the numbers upside down. In theory, it shouldn't have worked, but it caused the pair of 1N4148 silicon diodes to clip even harder and drive the LM308N op amp into a soaring high-gain sustain. What a beautiful accident for guitar players everywhere. They utilized a Tone control that was more of a backwards treble bleed potentiometer. What started out as a circuit similar to MXR's Distortion + turned into a revolutionary pedal classic. The large box versions were produced in 20 gauge sheet metal and featured the "Sound Inc" on the ProCo logo. It underwent many incarnations next with the heavier gage small box models(with and without led), Turbo Rat(different diodes), R2D2(rackmount), Juggernaut(for bass players), Brat(little brother), Vintage Rat(not), DeuceTone(2 for 1) and the Dirty Rat. Metallica had one on their pedal board in the early days. For more info on this device see the entire history at

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