Roots Radical: MXR's Distortion+ Through the Years

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Written by Nicholas Kula

True story: The team and I were discussing first entries for this column, and the Distortion+ headed up my short list of nominees. On my walk home from the meeting, I found a DIY pedal in the bushes outside a non-musical related establishment, complete with crusty potentiometers and weather-battered footswitch. When I got home, I cracked it open—lo and behold, a Distiortion+ clone. Serendipity!

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In 1979, Rochester New York's MXR introduced the Distortion+, a simple distortion circuit that revolutionized the industry. Drawing topological similarities to the simpler fuzz boxes of yore, the Distortion+ made the most with a small number of parts—18, to be exact. The result is and was a transcendent distortion box that has been copied hundreds of times and continues to serve as the basis for many boutique pedals in the present day. 

 

Schematic drawn by Nicholas Kula

Schematic drawn by Nicholas Kula

Much like, well, every single MXR pedal in the brand's original line, the Distortion+ launched "the distortion" offering of many startup companies of the era. The Ross Distortion borrowed heavily and liberally from the Distortion+, changing only the potentiometer values and the op-amp, while the DOD 250 likewise did little to separate itself from the original schematic, toying with a couple different component values and changing the clipping arrangement, yet leaving the topology alone.

 

Outside of the US, Europe and the Far East made hay with the circuit, releasing hundreds of variations. "Brands" like Coron, Marquis and Memphis sprung up everywhere and cannibalized not just the Distortion+, but all MXR pedals. These units were often built by one factory in their respective regions, where they were freely distributed to anyone that wanted them, resulting in a glut of the same pedal sold regionally under different names. These "brands" when turned around and exported them to the States, where they were offered to dealers at rock-bottom pricing, often forcing dealers to choose between their bottom line and customer brand loyalty. These imports eventually cut into sales, and in the beginning, MXR turned a blind eye.

 

Eventually, MXR had to come to grips with competing against the inundation of dirt-cheap imports, and designed them to sell at a cheaper retail price with the Commande line, featuring plastic enclosures and some parts that were prone to failure. Strangely, the Commande series did not feature an iteration of the Distortion+, opting instead for a Tube Screamer-esque "Overdrive." After the failure of the Commande series, MXR released the "2000" line, designed as a higher-quality version of each of its legacy products (and the Junior—swing and a miss). The 2000 featured the Distortion+, Ironically, the future-themed name of the latter would prove to be the company's swan song and MXR folded in 1984, just two years after the line's introduction. 

 

 When Jim Dunlop bought MXR, it revived the company's original designs (sans the Envelope Filter, c'mon guys), including the Distortion+, now sporting a neon-yellow case, standard LED, power jack and a brighter paint job. These new models featured a different clipping section, opting for more readily-available silicon parts in lieu of germanium devices. Though Dunlop made a slight detour with the "script" (named as such because of the cursive font found on the enclosures) reissue—a ProGuitarShop exclusive with vintage-correct parts—that silicon-equipped bright-yellow Distortion+ continues to be made today, largely true to the first circuit since none of the original parts are obsolete. 

 

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The crucial parts of the circuit are the 741 op-amp and the germanium clipping diodes. The 741 is a "low-fidelity" op-amp that many hi-fi purists would angrily denounce, but it's this mushy characteristic that plays so well with guitar. An unsung part of the topology lies within the four 1M resistors, one across the op-amp's pins but three affecting the bias voltage. The wide tolerance of the resistors made eons ago coupled with the large value biases each pedal differently, conversely affecting the tone. With that said, the sound of "script" Distortion+ units range from "good" to "great," and so "great" examples are oftentimes prized pieces of a respectable vintage pedal stable. 

 

The sound is purely additive, sounding at its best when fed into an amp that's on the verge of breakup, and several players across many genres used the circuit for their signature tones. Bob Mould of Hüsker Dü relied heavily on his "script" unit, with the Distortion+ used as a tonal building block, and Yngwie Malmsteen famously used the DOD 250, even getting his own signature model in DOD's waning days. Mike Schiedt of local boys YOB used a Ross Distortion until Black Arts Toneworks collaborated with him, releasing the Quantum Mystic, itself a Distortion+ rework with a three-band EQ. A bevy of other players, such as Jerry Garcia, Randy Rhoads and Thom Yorke, round out the esteemed guild of Distortion+ users over the years.

 

The Distortion+ is one of those circuits that you've heard even if you swear up and down that you haven't. Its presence in both classic and contemporary records is undeniable and vastly prevalent. Do yourself a favor and dig a little deeper—there's gold in them there hills. 

Joseph Rubenstein