The ProCo RAT is one of the most beautifully feral distortion boxes of all time. At its extreme settings, the RAT is a bringer of chaos—the sonic manifestation of an enraged Godzilla-Freddy Krueger-zombie werewolf fever dream. But, unlike our conjoined monster trio, you can control a RAT and use it for the noble pursuit of extraordinary guitar tone.
Founded by Charlie Wicks in 1974, ProCo Sound evolved from the ashes of The Sound Factory music co-op in Kalamazoo, Michigan. In 1978, ProCo engineers Scott Burnham and Steve Kiraly developed the first RAT—as a custom-order pedal—in a “rodent-infested” basement at the company headquarters. A year later, production RATs made the scene, and the distortion box eventually captured the sonically savage imaginations of guitarists such as David Gilmour, Jeff Beck, Robert Fripp, Joe Perry, Nuno Bettencourt, John Scofield, Bill Frisell, Sonny Sharrock, Kurt Cobain, Kevin Shields, Matt Bellamy and many others.
Pictured: ProCo RAT2 Distortion Pedal
Interestingly, the secret sauce of the RAT’s unique, ferocious and enduring distortion profile was down to a blissful blunder.
Burnham inadvertently soldered a 47k resistor, rather than a 470k resistor, into the op-amp gain section. As a result, the op-amp overloaded before reaching the diodes that were intended to clip and produce distortion. At the time, the concept of “op-amp distortion” was unique and pioneering, and distorting an already distorted signal provided the RAT with its signature yummy yowl and hostile wail.
Today, you can still wield that original op-amp distortion circuit like it was the ’80s (and beyond) or go for a more versatile RAT with enhanced low-frequency muscle. Here’s a peek at how you can RAT-ify the tonal authority of your pedalboard.
Table of Contents
Comparing RAT Pedals
A Guide to the ProCo RAT
The RAT Race
People Also Ask ...
Comparing RAT Pedals
|
Rodent Genus |
Basic Clipping Circuit |
Typical Current Draw |
Switching Method |
Controls |
Price |
|
OP-O7DP Op-amp |
1.6mA |
True bypass |
Distortion, Filter, Volume |
$119.99 |
|
|
OP-O7DP Op-amp |
11mA |
True bypass |
Distortion, Filter, Volume |
$99.99 |
|
|
Switchable, Stock or MOSFET |
5mA |
True bypass |
Distortion, Filter, Volume, Stock/Fat, Stock/MOSFET |
$179.99 |
Pricing as of December 2025*
A Guide to the ProCo RAT
Pictured: ProCo The RAT Circuitry
ProCo RAT2
Why It’s Grind-o-licious: All hail the original dark monarch of blistering buzz.
Things to Consider:
- Glow-in-the-dark graphics
- Accessible “no tools required” battery compartment
- Powered by 9V battery or optional power supply (sold separately)
Shop Now: ProCo RAT2 Distortion Pedal
The ProCo RAT2 features the 1981 circuit, which was the first revision since the pedal’s original 1979 mass-production run. This is the RAT tone that graced my pedalboard from the last gasp of the ’70s punk movement sound up to the explosion of new wave music and MTV. The steel chassis and tough-as-nails footswitch never failed throughout hundreds of gigs, and that resilience is present and accounted for in the RAT2 construction today. I wish I had the current pedal’s on/off LED indicator back in the ’80s, but if I forgot to turn off the RAT’s frenzied wrath after a solo, well, I simply considered it an added treat for the audience.
ProCo Lil' RAT
Why It’s Grind-o-licious: All of the savage glory of the ’80s-era RAT2 in a pedalboard-friendly “snack-sized” chassis.
Things to Consider:
- Glow-in-the-dark graphics
- Gig-tough metal chassis
- Needs 9V power supply (not included)
Shop Now: ProCo Lil' RAT Distortion Pedal
The ProCo Lil’ RAT gobbles up less than half the pedalboard space of the RAT2, while producing the same sonic carnage as the larger model. The miniaturization, however, does present a couple of performance notes. There’s no room for a battery, so the Lil’ RAT must be powered by an optional DC power cable (sold separately)—which shouldn’t be a concern if your pedalboard already has a power supply mounted on it. The tiny control knobs may be a slight annoyance if you need to quickly change sounds on stage during a solo or riff—but let’s be honest, how often does that really happen? Finally, if you wear Doc Martens to the gig, make sure your aim is true, or you may miss the Lil’ RAT’s little footswitch.
ProCo FAT RAT
Why It’s Grind-o-licious: It’s a hybrid mutant RAT with selectable midrange rage and beefed-up bass.
Things to Consider:
- Glow-in-the-dark graphics
- Accessible “no tools required” battery compartment
- Can operate at 9V or high-headroom 18V
Shop Now: ProCo FAT RAT Distortion Pedal
The more yard rats my pups can chase—and hopefully never catch—is big fun for them, and the added tonal versatility of the ProCo FAT RAT should deliver ample joy for you, as well. Based on 1985’s Whiteface reissue RAT, the FAT RAT offers two switchable parameters—each with an option to retain the pedal’s classic sound or enhance the tone. For players who want more warmth or boom, the Fat switch produces a simultaneous low-end boost and a high cut. Happily, lovers of midrange aren’t ignored in this version, as they can ping-pong between MOSFET (subtly scooped with smooth upper mids) and Stock (articulate and angry) settings.
The RAT Race
The sound of RATs—we mean the pedals—are still as relevant, exciting and terrifying as they were when the boxes started appearing on stage floors and pedalboards in the 1980s. The pedals are perennial top-sellers at Guitar Center, and exclusive colorways, such as last year’s White RAT, are massively popular, quick-to-sell-out specials.
Pictured: ProCo Lil' RAT Distortion Pedal
The innovative-for-its-day RAT circuitry also continues to be imitated, augmented and reengineered by various pedal manufacturers—quite the salute to the genius of the original design. You can find bona fide RATs and RAT-style rethinks scurrying around our website or at your local Guitar Center. In addition, as RAT pedals tended to evolve ever so slightly from batch to batch, adventurous types should seek their buzzy bliss in our collections of used and vintage RAT pedals. As always, if you have any questions, our Pro Gear Advisers can supply the knowledge and support you need.
People Also Ask ...
Pictured: ProCo FAT RAT Distortion Pedal
What was the original ProCo RAT op-amp?
The ProCo RAT was introduced with an LM308 op-amp, which was phased out starting in 1995, after Texas Instruments declared it “obsolete” in 1993. RAT2 pedals manufactured after 1996 most likely contain the replacement T.I. OD07DP op-amp. And lest “vintage-design disciples” maintain the LM308 had magical attributes that made pre-1996 RATs sound better, according to JHS Pedals founder Josh Scott—who is also a stompbox historian and RAT myth smasher—the “response, slew rate and frequency attenuation (of the LM308 and OD07DP) are identical. They are identical in performance and sound.”
Can you use a ProCo RAT2 as an overdrive pedal?
Our question is: “Why would you?” But if you’re in a pinch and need to figure out a way to diminish the distortion on a RAT2, try adjusting the Distortion knob to its lower settings and play with the Filter control to tame any scorching highs. Some pedal forum users suggest parking Distortion at 9 o’clock and Filter at 2 o’clock as a starting point for low-gain and overdrive sounds.
How big is the ProCo RAT family?
The RAT eventually birthed a slew of variations—some of which are no longer available (although you may be able to find some used models). Family members past and present include Turbo RAT (launched 1989), You Dirty RAT (launched 2004), Deucetone RAT (launched 2002), Juggernaut (1979–1983, reissued 2003), Roadkill (a Guitar Center exclusive, 1996–2001) and BRAT (1997–2001).