Pro Co RAT

While experimenting with his circuit however, he accidentally used the wrong value resistor to bias the operational amplifier, driving it into heavy distortion.

Author Pagan Kennedy describes Burnham's invention as follows:[3] "One day, as he was soldering parts, he picked up a resistor of the wrong size -this was his lucky mistake- and attached it to a circuit board.

He immediately recognized this as a major discovery, and he built that sound into a distortion pedal he named the Rat.

[5] Only twelve of these pedals (including one prototype), commonly referred to as the "Bud Box" RAT, were produced.

[5] 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.

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.

It then moves on to the gain stage, which is based around a single opamp, originally the Motorola LM308 (switched to Texas Instruments OP07DP around 2002–2003).

The 'Turbo RAT' pedal uses red LEDs for this purpose (red LEDs have about a twice as high forward voltage as the original silicon diodes), while the 'You Dirty RAT' pedal uses 1N34A germanium diodes (clipping at a much lower forward voltage).