Effect History: Legendary Overdrive Pedals – Part 1

Effect PedalProco Rat

The Proco Rat is one of the most legendary overdrive pedals and has been used by countless guitarists.
Jeff Beck, Joe Walsh, Mike Campbell, David Gilmour, Thom Yorke, Bill Frisell, John Scofield, Dave Grohl, Andy Summers, Kurt Cobain, James Hetfield, Joe Perry, and actually everybody who played his guitar in the 90s.
The first Proco Rat has been produced in 1978 and still today this stompbox is manufactured almost unchanged.
The enclosure of the Rat is nearly indestructible. Rubber feet guarantee a safe stand, the battery compartment can be opened easily, and it also has a power supply jack.
By three knobs you can control distortion, filter and volume.
While the first Rat pedals had no status LED, you can find this feature on every version that was built after the end of the 1980s.


The sound of the Proco Rat is unique. Built up around the LM308N (at those days a high-quality medical technique product), the Rat was one of the first pedals with true bypass.
Allegedly because of a mistake concerning a certain part (470 Ohm instead of 4700 Ohm) the Rat got 70db gain instead of the planned 50db.
But because of the limitation of the OP amp this theoretical value is never reached.

For the reason of its inertia, the LM308N also influences the frequencies of this overdrive pedal for it is unable to deal with frequencies above 5.3 KHz.
The diodes hartclipping and the internal filters create an emphasis of the mids at 1KHz.
This frequency causes that the guitar will cut the mix.
The Klon Centaur also emphasizes this frequency.


The clear structure of the pedal is perfect for modifications.
The most simple mod replaces the diode clipping by a LED clipping (like the Turbo Rat).
Or you can modify a Rat2 into a first-version-Rat or reduce the gain and emphasize the bass to get a better low gain sound.

Even today the Proco Rat has got the right to exist and in my opinion every guitarist should have used a rat once.
Unfortunately, the current models sound a bit different compared to the earlier “made in USA” models.
Because of the different IC they sound more modern.
Speaking for myself, it is worth it to look for a 1980s or 1990s Rat.