The Noise Room got a look at the FAT RAT distortion pedal at the Rat Distortion booth at NAMM. Built by ProCo Sound, it packed switchable clipping between Silicon and Mosfet settings, a FAT Switch for a significant low-end boost, and a socketed op-amp for players who wanted to swap chips and experiment with the tone.
The FAT RAT was based on ProCo’s Whiteface Reissue platform, adding a bass-enhancement circuit and a clipping section that hadn’t shown up on a RAT before. It has since been discontinued, and its take on switchable clipping ended up as one entry in a much longer history rather than a lasting fixture of the line.
That history goes back to 1978, when ProCo engineers built the first RAT prototype, called the Bud Box, in the basement of the company’s Kalamazoo, Michigan factory. Only a dozen were made. By 1979 the pedal was in full production, in the distinctive wraparound enclosure that is still recognizable on pedalboards today, largely unchanged across more than four decades of players.
Rat Distortion, the brand that grew out of that original circuit, has kept several versions in active production: the RAT2, Turbo RAT, Deucetone RAT, and You Dirty RAT, most recently joined by a smaller-footprint version called the Lil’ RAT, built for guitar players who want the RAT sound without the larger footprint. Each one takes a different path through the same core circuit the FAT RAT drew from, whether through diode swaps, LED clipping, or op-amp changes.
A NAMM booth is where a lot of that variation gets tried out side by side, pedal by pedal, before anyone commits to what goes on the board. The FAT RAT was one especially flexible stop along that line, built for a player who wanted every clipping option available in a single box.
