Dirty Rat

Pro Co RAT

The Pro Co RAT is a guitar Effects pedal produced by Pro Co Sound. The original RAT was developed in the basement of Pro Co's Kalamazoo, Michigan facility in 1978. Numerous variations of the original RAT pedal are still being produced today.

The basic RAT has changed in appearance over the years, but its tone has remained largely the same,although there is a general consensus that the mid 80's versions are superior sonically. Pro Co has also introduced tonal variations of the RAT, including the Turbo RAT, You Dirty RAT, and Juggernaut Bass RAT, among others.

The Pro Co RAT became very popular in the early 1980s, thanks in part to notoriety gained by its use by artists such as Jeff Beck and Joe Walsh. Since that time, the RAT has been used by some of the most influential guitarists in the world. This list includes David Gilmour, Jeff Beck, Kevin Eubanks, Thom Yorke, John Scofield, John Christ, Dave Grohl, Kevin Shields, Andy Summers, Thurston Moore, Graham Coxon, Jerry Cantrell, Kurt Cobain, James Hetfield and Krist Novoselic


The origins of the Pro Co RAT can be traced back to the mid-1970s, when Pro Co engineers Scott Burnham and Steve Kiraly repaired and hot-rodded existing distortion pedals, such as the Dallas-Arbiter Fuzz Face. Burnham decided he could build a superior product from the ground up, and designed the RAT pedal.

In 1978, the RAT was being built as a custom-order product. Only twelve of these pedals, commonly referred to as the “Bud Box RAT,” were produced. Each pedal was built in a standard project box, hand painted, and hand drilled. By 1979, as the pedal became more popular, Pro Co began mass producing them. This iteration was built in a custom designed, rectangular sheet-metal enclosure. In 1984, Pro Co switched to a smaller, U-shaped enclosure. Finally, in 1988, the RAT 2 was introduced, which included an on/off LED. Various RAT 2 circuit board layouts and wiring configurations have surfaced in the last few years, including the noted "RAT3 version A and B" all under the RAT 2 moniker. The RAT 2 model is still available today, but is now made in China for Proco Sound by Neutrik.

Other models of RAT products include:

  • Juggernaut (1979)
  • R2DU (1984)
  • Turbo RAT (1989)
  • Vintage RAT (1991)
  • BRAT (1997)
  • Deucetone RAT (2002)
  • Juggernaut Bass RAT (2003)
  • You Dirty RAT (2004)

How it works

The Pro Co RAT is a distortion pedal with a very simple circuit, based around a single op-amp the LM308. The distortion is produced using a variable gain circuit with diodes shorting the output to ground to produce hard clipping of the input waveform. This distortion stage is followed by a passive tone filter and volume control. This is the same scheme as the Boss DS-1 distortion pedal, although major differences between the two circuits, and therefore the sound of the two pedals, exist. The most popular RAT pedal, the RAT2, features true bypass switching.

Versions of the RAT

Robert Strand's webpage lists the various RAT versions produced over the years. Pro Co also has a RAT History page on their website.

Current Product Line

  • Rat 2 (Made In China)
  • Turbo Rat
  • Deucetone Rat
  • You Dirty Rat
  • Juggernaut Bass Rat

Discontinued Products

  • "Bud Box" RAT
  • The RAT
  • The RAT (version 2)
  • Juggernaut
  • "Small Box" RAT
  • Vintage RAT (no LED version)
  • BRAT

Non-RAT pedals produced by Pro Co

  • Pro Co Solo

Popular Modifications to the RAT

The RAT is a popular pedal for modifying. Some of the possible modifications include:

  • Resistor Mods: The Ruetz Rat mod which involves simply cutting the 47ohmresistor to disengage half of the drive circuit. Gain is reduced somewhat and the bass is no longer attenuated. This can translate to thicker (fuzzier) bass response at the expense of less distortion.
  • Toggle Switches: The Mightier Mouse mod involves a 3-way switch to select between Rat2 (clipping via OPAMP only), Turbo Rat (clipping via LEDs), and MOSFET clipping modes. It also shows an alternative to the Ruetz Rat mod using a potentiometer or trimpot to replace the resistor instead of simply cutting it.
  • Diode Removal: Removing one of the two silicon clipping diodes for a volume boost crunch tone.
  • Chip Substitutions: The original RAT pedals featured the LM308 IC which is now quite expensive. Recent Rat pedals now feature the Texas Instruments OP07DP. Other OPAMP ICs that people try include: NE5535A, NE5534AP LM741, TL071 FET-OP. Many install an IC socket to enable easy swapping of ICs, very much similar to what people do with the Ibanez Tube Screamer.
  • Capacitor Mods: "softening" ceramic caps replaced with silver mica or metal film caps for better tonal fidelity.
  • Power Adapter: 2.1mm (Boss-style) 9vDC adapter socket mod. Because the tip on the Boss-style adapter is negative, one needs to install a plastic 2.1mm (switching) socket to avoid shorting out against the RAT2's steel chasis.
  • Robert Keeley Electronics does a popular mod involving replacement of the existing chip for an original LM308 IC, a capacitor upgrade (using film and tatalum capacitors) to improve bass response and a 3 way mode switch. The first mode is the Classic RAT which is the original RAT circuit. The second mode is the Phat RAT which has an extra diode added to the original circuit in attempt to achieve a more tube-like sound. The final mode is the Mighty Mouse in which a diode is removed from the original circuit causing it to behave more like a boost pedal.
  • Electronics modders Vodka Mods perform a popular RATsputin mod that includes dual toggle switchs to the drive and clipping sections, a Texas Instruments NE5534AP chip upgrade and an extra case mounted potentiometer, which allows maximum control over tonal variables. More info is available at their website.
  • Jack Orman, includes many mods and an available e-book at his website.


External links

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