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 what would become "The RAT" pedal. Burnham began work on his circuit as early as 1974, right around the same time hard clipping distortion circuits were starting to enter the market. While experimenting with his circuit however, he accidentally used the wrong value resistor to bias the operational amplifier, driving it into heavy distortion. "Opamp distortion" as it has come to be known was a completely novel idea at the time and, combined with the diode clipping section, allowed for much more aggressive distortion than was available at the time. 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. The machine began shrieking and moaning. And that's how he heard a new sound; it was beautiful, haunting, ugly, and full of soul. He immediately recognized this as a major discovery, and he built that sound into a distortion pedal he named the Rat. Attached to a guitar, the Rat turned every note into a blast of outrage".
In 1978, "The RAT", named because of the rat infested basement in which it was designed, [4] was being built as a custom-order product. [5] Only twelve of these pedals (including one prototype), 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. [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. Between 1979 and 1980 there were several cosmetic changes to the pedal as Pro Co worked to source knobs and print the labels on the pedal, but the circuit remained largely unchanged. In 1981 the Rat saw its first circuit change. The tone control, which allowed the user to lower the volume of the treble frequencies as they turned it counterclockwise, was reversed to turn the treble down as the knob is turned clockwise. From an electrical standpoint, this change made no difference, but it is believed that the change was made through user feedback in an attempt to make the users perceive the effect as less harsh. [4]
In 1983, Pro Co switched to a smaller, U-shaped enclosure.Finally, in 1988, the RAT2 was introduced, which included an on/off LED that utilized a new "millenium bypass circuit", which has become the industry standard for pedal switching circuits. [4] The screen printed labels were replaced with glow in the dark mylar. 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. In 2019 Pro Co switched to an industry standard PSA adapter from their 1/8" adapter. Despite the high number of Rats released throughout the years, the circuit has remained very similar to the original schematic.
Other models of RAT products include: [5]
- R2DU (1984–1988)
- Juggernaut (original) (1979–1981)
- RAT2 (1988–present)
- Turbo RAT (1989–present)
- Vintage RAT Reissue (1991–2005)
- BRAT / Roadkill (1997–2001)
- Deucetone RAT (2002–present)
- Juggernaut (reissue) (2003–present)
- 25th Silver Anniversary RAT (2003)
- You Dirty RAT (2004–present)
- SOLO (2006–present)
- '85 Whiteface RAT Reissue (2010)
- FATRAT (2014–present)
- Lil' Rat (2021–present)
Circuitry
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. [5] All except the power supply directly interact with the guitar signal. The signal enters into the pedal, travels through a bandpass filter that filters out high and low frequency content from the signal.
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 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. At lower gain levels the distortion is produced entirely through the diodes, but at higher gain levels the opamp begins to distort as well. Originally, 1N914 diodes were used, which were later replaced with 1N4148 since RAT2. 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). [5] [6]
The distortion stage is followed by a passive "reverse" tone filter and volume control.
This circuit has remained almost entirely untouched throughout the manufacture of the RAT and RAT2. Other versions of the RAT are near identical to the RAT2 except for changes to the clipping diodes, different enclosures, or the addition of new controls.
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