Designed in the early '70s, the MXR Distortion + is an incredibly simple—yet highly effective—distortion pedal. Although the name might suggest otherwise, the Distortion + has a relatively mild sound. When used with high-output pickups and a cranked tube amp, it can dive deep into heavy metal territory, but the smooth, subtle tones it produces at lower gain settings attracted a wide variety of guitarists outside of the metal scene.
The Distortion + uses a single op-amp and two germanium diodes for clipping. Its an incredibly simple pedal that originally ran only off of a 9V battery, and until the 1981 iteration, it didn't even have an LED to let you know it was activated. Just two controls: volume and distortion. Famously, the treble content increases subtly as you increase the distortion knob.
The MXR Distortion + has been copied numerous times (most famously by DOD as the 250 Overdrive/Preamp), and the versatile clipped tones it produces are heard on a wide variety of recordings. In the '70s, players from Randy Rhoads to Jerry Garcia used this pedal. While the reissues aren't bad, they simply don't compare to the sound of a vintage original.
This 1981 MXR Distortion + is in good condition for its age, and it functions 100% as it should with no issues whatsoever. There are some minor chips in the paint (see photos), and one of the four screws is missing. Other than that, it has been nicely preserved over the years, and it sounds fantastic. This is the 1981 circuit, so it features the MXR "block" logo, a jack for a 9V adaptor, and an LED indicator.
It's easy to understand why the Distortion + became a reference pedal for boutique effect designers—it sounds great, and its tone has held up well over time.