Back in the olden days of late seventies, Scott Burnham, bearing the title of Pro Co Sound Inc.’s “Hippie in Charge of Technology”, toiled away in a rat-infested basement of his employer’s facility in Kalamazoo, Michigan. And while the customers browsed the relatively unheard-of company’s various electric guitar accessories in the showroom above, Scott, like a true sonic alchemist, was on a sacred quest of distilling the pure essence of guitar distortion.
And although there were quite a few distortion pedals available at the time (bear in mind, this was happening when the members of Black Sabbath were already well-established as the kings of heavy music with countless other bands following suite), Scott wasn’t satisfied with what was already out there, and sought a pedal that would make a sound to fill up arenas with its hellish roar, a pedal with a sharp and nasty bite that would really make the hair on the back of your neck stand up.
During that time, countless attempts were made, but not one resulted in the effect that Scott desired, and Pro Co slowly began to feel disheartened with his project. However, as fate would have it, while working on yet another attempt to make One Pedal To Rule Them All, Scott accidentally attached a wrong resistor and attached it to the circuit board – and the effect it produced blew his mind.
Since its arrival on the electric guitar gear market, Pro Co’s RAT made an impact that shook the very foundations of rock. Countless musicians flocked to the pedal’s amazing distortion potential, and the RAT burrowed its way into the annals of rock and metal as bands such as Metallica, R.E.M., Aerosmith, Nirvana and many more began using it as a staple of their sound. But what does exactly Pro Co’s RAT pedal contain, and how did it change throughout the years?
The Rat soon became very sought after for its prodigious ability to provide both filthy distortion and very high sustain. Essentially, the RAT pedal uses two symmetrical diodes to ground after the gain stage, producing the final effect of a hard, square-wave clip. The first models used a LM308 op-amp with a slow response, which hard-clipped both the op-amp as well as high- frequency attenuation, resulting in the RAT’s signature aggressive distortion. The LM308 also has a strong impact on the EQ, by letting frequencies below 500Hz run wild, while clipping it off almost completely above 5kHz or so.
Traditionally, the RAT contains three knob controls for distortion, filter and volume. The pedal’s distortion is surprisingly versatile, since it shines on higher gain but remains reliable in low-gain settings as well.
The filter control represents your run-of-the-mill low-pass filter, which makes a square wave signal with decreased bass, while bringing the signal closer to a triangle shape with the bass flowing freely.
Finally, the volume control surprisingly doesn’t affect the tone due to a JFET buffer thrown in between the two circuit blocks, with the output block being a 100K pot that blends the signal. Now that we’re more familiar with the RAT’s guts, let’s go over a bit of history.
Despite Scott Burnham’s amazement with this unique sound he accidentally came up with, during those early days in 1978 there were still serious doubts about if and how much the newly-born RAT would be commercially viable, and, as a result, it was never intended to be mass produced.
Going under the moniker “Bud Box”, only twelve of these original RATs were ever made. You could get one only on direct demand, and all were made by hand. The “Bud Box” came in a humble-looking black casing with the logos of Pro Co, the RAT pedal, and the name of its place of origin printed in bright florescent silk-screened font. The “Bud Box” contained all three iconic knobs, labeled “Distortion”, “Tone” (stand-in for EQ), and “Volume”.
The reason for apparently only twelve people wanting one could probably be found in the fact that this first incarnation of the RAT was kept firmly inside Pro Co Sound’s closet rather than in there being no interest for such a pedal – but rather the opposite; as we’ll see, everybody needed a RAT; they just didn’t know it yet.
Apparently, Pro Co changed their opinion about this pedal’s commercial viability as early as 1979, and released “The Rat” into the vast wilderness of the wider guitar gear market. This iteration was mass produced from 1979 to 1981, and this was the time when “The Rat” became to take the world by storm.
Much better-looking than its predecessor, “The Rat” was cased in custom 20 gauge wrap-around enclosure that gave off an air of durability and extravagance. The three knobs retained their names, albeit in a much discrete print. The logos, now more elegantly designed but in the same silk-screened print, were enclosed in a neat little rectangle beneath the controls.
Although the RAT would more or less keep the same spirit throughout its various iteration, there’s one technical aspect of “The Rat” that stands out – namely, the “Tone” knob would increase high frequencies when turned clockwise, whereas the later models functioned the other way around.
As the Rat fever was spreading through the music world, the pedal responsible for this mass infection went through yet another round of elegant streamlining of its design. The casing was now a gorgeous ink black, and the “Rat” logo switched its last two letters to lower case, fully embracing its name (if only for a little while).
The “Tone” knob was now titled “Filter”, and, as already mentioned, it would cut the high end the more it was turned clockwise. The Rat (ver.2) would have a relatively short run, from 1981 to 1983.
Input Impedance: 1 MOhm
Output Impedance: 1 kOhm
Filter: 6dB/Oct Low-Pass
Connectors: 1 x Power Input 1 x 1/4" Input 1 x 1/4" Output
Power Requirements: 9V Battery or External Power Supply (Not Included)
Dimensions (HxWxD): 3.1 x 3.5 x 4.1" (79 x 89 x 104mm)