The mighty, mighty ProCo Rat


My favourite pedal ever… an article by John Mercer & Tony ‘Guitarnerd’ Jackyl

Originally built in 1979 and only as a custom order, The Rat started out as an idea by Pro Co engineers tired of modding existing fuzz and distortion pedals. Believing they could make a superior product from scratch what we know as the Pro Co Rat made its loud screeching distorting debut.


A pedal with surprisingly adjustable tones, the range can easily be shifted from mega fuzz distortion to middle of the road tuesday night blues. A classic used by a wide range of guitarists from Buzz Osborne to Thom Yorke, James Hetfield to Andy Sumners, even fucking Nuno from Extreme gets his hand in there now and then (plus guitarnerd has been seen rocking one on the bass).

Instead of the usual options like “tone” or “eq” the Rat has a “filter” knob that acts exactly as it says. Filtering the gain from a mid scooped tone through to a much fuller bassier distortion. But the filters not gonna stop everything. This distortion has bite, while you can get away with lighter tones while the distortion is winded down, turn it up any more than a quarter of the way and it’ll rip balls straight through pants.

What most people know and love as the Pro Co Rat these days is actually a RAT2 the main difference aesthetically is the instilation of an l.e.d. so you know when its on (though if you can’t tell from the sound something is pretty wrong). Other differences are more dramatic. There have been a few different circuit board set ups and variations on parts, and of course everyone has there favourite period of RAT, swearing that certain pedals made at certain times have a better sound etc etc. There have also been many dofferent models made with names like “Turbo Rat”, “You Dirty Rat” “R2DU” and the list goes on. For me its just the RAT and I’m stoked on it.


Thanks John. As John mentioned, a big part of my bass sound is a vintage Rat. My holy grail of bass sounds (inherited from the previous bassist, now guitarist from Sixfthick, Dan) is a mix between JJ Burnell from The Stranglers, David Wm. Sims from Jesus Lizard and the bass sound from ‘Wolverine Blues’ by Entombed. To achieve a close proximity to this sound I need 5 ingredients… my 1972 Fender P-Bass (now retired, replaced with my 1977 Ibanez Black Eagle), an early 80’s GK800RB bass head (now replaced with Genz Benz Shuttle 600 due to it’s weight.), an Ampeg 4×10 (better yet… Ampeg 8×10 if I can borrow one and get someone to lug it for me), a set of stainless steel bass strings (they just sound so frikken’ good) and finally my trusty, Tym modified vintage ProCo Rat.


On the outside, it looks like any regular vintage Rat. I like this model better than the Turbo Rat, which I think sounds less warm and too fizzy. I long ago found my favourite settings on these things (distortion at 11 o’clock… depending on the bass bin I’m playing through, filter at around 12 o’clock… depending on the age of my strings, and volume at full). If I’m playing through my bass head and not borrowing someone elses, I can get my sound in about 4 minutes. I find that this pedal likes LOUD solid state heads better than tube heads, which sound too woolly. Ampeg SVT’s aren’t one of my faves.

Me being me, I thought I could get that little bit closer to the bass sound in my head, so I took my beloved Rat to Andrew (former pedal guy at Tym’s) and asked him to see if he could shove a Tym Big Bottom pedal into it. Andrew said he’d see what he could do, and this is what I got back… FrankenRat!!!


It’s got 2 circuit boards stacked on top of each other, with a cutdown Big Bottom circuit sitting on top of the Rats. It’s not pretty, but man it sounds sweet! Andrew moved the volume control and replaced it with the Big Bottom’s blend control, so I can blend more of my amp’s clear bottom end into the pedal’ sound. There’s also an LED mod done by Cardboard Tube Samurai (local pedal tinkerer) that adds to it’s sound. It crisps up the sound a little, but not too much. I unscrewed the switch and it sits inside now in my preferred position, as I kept bending it in my gigbag.


After a while I moved the volume knob from the inside to the back, as I wanted to be able to adjust it if I ever needed to (which I haven’t had to yet… you never know, though). One day I’ll get around to actually screwing it in and putting a knob on it. It rattles around a bit at the moment… As I said, this pedal isn’t pretty. Oh, the battery is running loose in there too. Again, one day.


About 4 years ago, my Rat was stolen (actually I left it on stage at a gig in Melbourne… I got it back though). In the time that I was Rat-less, I asked Tim if he had any Rat’s for sale. He said he didn’t, but he had an Ibanez Fat Cat, which is exactly the same pedal. Apparently Ibanez made an exact replica of the Proco Rat, named it the Fat Cat, got a cease and desist from Proco and stopped making them. I was a bit dubious as I’m a devoted Rat disciple, but I plugged it in, moved the knobs to my settings (11, 12, full) and BAM!… there was my sound. I was shocked. Here was a Rat in a pedal the size of a Boss pedal. This pedal became my touring pedal for a while until I got my Rat back. I still have it and apart from a new switch, it’s a dependable, fantastic sounding pedal. It’s now my go-to pedal when I’m playing someone elses guitar amp. After so many years playing bass with my Rat, I forgot how killer a guitar pedal it is.