The Pro Co "The 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. Pro Co has also introduced tonal variations of the RAT, including the Turbo RAT and You Dirty RAT, among others. The Pro Co RAT became very popular in the early 1980s, thanks in part to fame gained by its use by several artists, including Metallica, R.E.M. and Weezer.
History
The origins of the Pro Co "The 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. In 1979, Pro Co began mass-producing them. This iteration was built in a custom designed, rectangular sheet-metal enclosure, with an L shaped removable top/back section giving access to the internals. The top panel was labeled with Pro Co Sound "The RAT" and the three control knobs as Distortion, Tone and Volume. In 1983, Pro Co switched to a smaller, U-shaped enclosure. Finally, in 1988, the RAT2 was introduced, which included an on/off LED. Various RAT2 circuit board layouts and wiring configurations have surfaced in the last few years, including the noted "RAT3 version A and B" all under the RAT2 moniker. The RAT2 model is still available today, but in 2008 production moved to China and is now manufactured by Neutrik for Pro Co Sound. Other models of RAT products include:
The Pro Co "The RAT" is a distortion pedal with a quite simple circuit, which can be broken down into four simpler blocks: distortion stage, tone control, output stage and power supply. The design is based around a single opamp, originally the Motorola LM308. The distortion is produced using a variable gain circuit with diodes shorting the output to ground at a certain voltage level to produce hard clipping of the input waveform. Originally, 1N914 diodes were used, which were later replaced with 1N4148 since RAT2. The 'Turbo RAT' pedal uses red LEDs for this purpose, while the 'You Dirty RAT' pedal uses 1N34A germanium diodes. The distortion stage is followed by a passive 'reverse' tone filter and volume control. The general design is very similar to the Boss DS-1 distortion pedal. A major difference is the opamp used. Known for its poor slew rate, it largely accounts for the sonic difference between the two pedals.
Non-RAT moniker pedals currently produced by ProCo
Solo, Scoop control, Tone
Discontinued products
"Bud Box" RAT
"Big Box" RAT
Juggernaut RAT size enclosure, Right side: 'Mix', Master Volume and on the Left side: Amount
"Small Box" RAT
R2DU
BRAT / Roadkill
Vintage RAT Reissue
'85 Whiteface RAT Reissue
Special Runs
IKEBE 40th Anniversary: All-white RAT2 pedal with black lettering, white knobs and a bright blue LED.
25th year Silver Anniversary Rat: "Big Box" pedal in a distinct silver coloured stainless steel enclosure with the tagline "25 years of Grunge".
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 47 Ωresistor to disengage half of the drive circuit. Gain is reduced somewhat and the bass is no longer attenuated. Additionally, the 560 Ω resistor controlling the lower half of the distortion filter can receive similar treatment. Either mod will translate to a thicker bass response at the expense of losing distortion.
Toggle Switches: The Mightier Mouse mod involves a 3-way switch to select between RAT / RAT2, Turbo RAT, and FAT RAT modes. It also shows an alternative to the Ruetz RAT mod by using a potentiometer or trimpot to replace the resistor instead of cutting it out of the circuit.
Diode Lift: Removing one of the two or both clipping diodes results in a volume boost with a crunchier tone.
Chip Substitutions: The original RAT pedals featured the rare Motorola LM308 opamp, which is now quite expensive to acquire. Recent RAT2 pedals nowawadays feature the widely available Texas Instruments OP07DP. Other opamps that people try, include: the CA3130EZ, the NE5535A / NE5534AP, the LM741 and finally the TL071 / TL081. Many RAT modders install an opamp socket to enable easy swapping of opamps, which is similar to what people do with the Ibanez Tube Screamer circuit.
Capacitor Mods: "softening" ceramic caps replaced with silver mica or metal film caps for better tonal fidelity. These include the 30 pF cap riding the opamp chip and the single 100 pF cap.
Power Jack: 2.1 mm 9 V DC adapter socket mod. Because the tip on the BOSS-style adapter is negative, one needs to install a plastic 2.1 mm socket to avoid shorting out the barrel of the plug against the RAT's steel chassis.
