An original MXR Innovations distortion plus pedal from 1979, block logo, without LED and battery-only operation (no AC Adapter).
MXR Distortion + on a guitar pedalboard. Distortion + is the yellow unit on front of the pedalboard.
The MXR Distortion + ("Distortion Plus") is an overdrive pedal originally designed in the 1970s by MXR Innovations. Although its name includes "distortion," it has a rather mild sound and essentially the same circuit as many overdrive pedals (e.g. DOD 250). The pedal uses a single opamp and a pair of germanium diodes to ground for clipping in a very simple configuration with only Output and Distortion controls, no tone control; the pedal uses no discrete transistors. Turning up the Distortion control increases the amount of distortion and at the same time cuts some bass from the signal. This pedal is perhaps best known for its crunchy heavy metal sound that was featured by Randy Rhoads in his work with Ozzy Osbourne. Jerry Garcia of the Grateful Dead used this pedal exclusively for distortion in the late 1970s. Bob Mould of Hüsker Dü also used the Distortion + as part of his trademark guitar sound. Dave Murray of Iron Maiden has used Distortion + since the early 1980s. Thom Yorke of Radiohead has included the + for many of his signature distortion sounds, using a variety of guitars to achieve various tonal options.