audiobriefs
8:41in productionCh. 1 · What it is/ 8:41 · ceiling 15 min
Effects & pedals

Pro Co RAT

The RAT doesn’t shape tone—it smashes it into something loud, fast, and unapologetically crude.

The Pro Co RAT is a distortion pedal for electric guitar, first prototyped in 1977 or 1978 and entering full production in 1979. Its distinctive aggressive distortion stems from an accidental 47 ohm resistor substitution that increased op-amp gain, combined with diode-based hard-clipping. It uses an op-amp to amplify and diodes to limit the signal.

Chapters & takeaways5
  1. 0:48
    What it is

    It is a distortion pedal for electric guitar—not overdrive, not fuzz, not boost.

  2. 2:07
    How it works

    A 47 ohm resistor mistake and diode clipping define its signal path.

  3. 3:09
    Why it mattered

    It made aggressive distortion possible years before others caught up.

  4. 4:00
    Where and when

    Born in a rat-infested basement in Kalamazoo, prototyped in 1977 or 1978, mass-produced from 1979.

  5. 5:33
    The version you’ll buy

    The RAT2—released in 1988—is the current production model.

Worth your time?

Yes. Use the whole thing.

4.5/ 5
What works
  • aggressive, saturated distortion
  • tight compression
  • immediate response to picking dynamics
  • cutting presence in a dense mix
What does not
  • clean up with guitar volume rolls
  • offer mid-scoop or bass roll-off controls
  • deliver subtle breakup or low-gain warmth
Use it if
  • guitarists who prioritise immediacy, cut, and saturated texture over nuance or dynamic range
Skip it if
  • players needing touch-sensitive overdrive or studio-grade transparency
The written brief1 min read

What it is and what it was built for

It is a distortion pedal for electric guitar, built in Kalamazoo, Michigan, to produce saturated, cutting distortion.

How it works, in terms a player would use

It amplifies the guitar signal with an op-amp, then hard-clips it using diodes connected to ground. A 47 ohm resistor—accidentally substituted for 470 ohms—biases the op-amp for higher gain.

What it does better than anything else

It delivers consistent, high-gain distortion with immediate response and tight compression—more aggressive than distortion pedals available before 1979.

What it does badly

It does not clean up well with guitar volume rolls. It lacks mid-scoop or bass roll-off controls. It cannot deliver subtle breakup or low-gain warmth.

What people made with it

Players used it for punk riffs, grunge leads, and alternative rock rhythm tones—especially where rawness and presence mattered more than fidelity.

Who should use it, and who should not

Guitarists who prioritise immediacy, cut, and saturated texture over nuance or dynamic range should use it. Players needing touch-sensitive overdrive or studio-grade transparency should not.

Is it worth your time

Yes—if you want aggressive, saturated distortion that cuts through a mix and responds sharply to picking dynamics. No—if you need clean boost, transparent overdrive, or fine-grained tonal shaping.

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8:52
Watkins CopicatWatkinsThe Watkins Copicat is a valve-based tape echo unit introduced in 1958. It features three replay heads, a selector switch, and a feedback loop for variable echo-repeat. It was designed to be simple, affordable, and portable. It was one of the first commercially available tape delay units and preceded other major European echo units. The first production run of 100 units sold out on the first day.
9:18
Fuzz FaceArbiter · 1966The Fuzz Face is a minimal, high-character fuzz pedal built for affordability—not precision. Its two-knob interface and six-component design deliver immediate, touch-sensitive distortion, especially with NKT275 germanium transistors. But its crude biasing makes germanium units thermally unstable. Silicon versions trade warmth for harshness and reliability. It excels at organic, swelling fuzz tones shaped by the player—not the pedal.
8:18
Maestro FZ-1 Fuzz-ToneMaestro · 1962The Maestro FZ-1 Fuzz-Tone is the first widely marketed fuzz effect. Introduced in 1962. Achieved mainstream impact in 1965 via Keith Richards on 'Satisfaction'. Uses three germanium transistors. Powered by two 1.5V batteries (later one). Responds directly to input amplitude. Temperature sensitive. Delivers brass-like tones. Integrated into Gibson EB-0F basses circa 1964. Revised as FZ-1a in late 1965.
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