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MXR - Distortion +

MXR Distortion+

General information:

The MXR Distortion+ was designed by Keith Barr (former President and co-founder of MXR Innovations) in the early 1970s and it has definitely made it's mark in the history of music since then, proving its status as one of the great classics in the expansive distortion world. Great guitar legends like Randy Rhoads (Ozzy Osbourne) and Bob Mould (Hüsker Dü/Sugar) have made the Distortion+ part of their trademark guitar sound and it has found its place on countless recordings throughout its almost 40 years history, musically ranging from mellow pop music to hard rock/heavy metal.

Slightly deviating from what the name "distortion+" would let you expect, the sound of the pedal is more an overdrive-type of sound ranging from low-volume mild distortion, over to a warm, tube-like overdrive, all the way to a crunchy, pronounced fuzztone with lots of sustain with the controls maxed out. The versatility of the sound is amazing considering the simplicity of the unit, producing a variety of sounds suitable for various musical styles from classic rock to scooped heavy metal.

As for the company behind this pedal, MXR (MXR Innovations) was one of the most proficient manufacturers in the effects industry in the late 70's and early 80's, playing a central role in creating the industry of electric guitar effects as we know it today. MXR was the largest US effects company and their original pedals and rack gear are still highly sought after today, neary 35 years later.
In the mid 80's, despite it's strong market position MXR was hard-pressed due to the incoming wave of effects from the far east (i.e. Boss and Ibanez), and was forced to give up the manufacturing of effects pedals in 1984. The same fate became also Electro Harmonix, who was propably the strongest US rival at that time. In 1987 the MXR brand was purchased by Jim Dunlop, who started making reissues of the old line of effects and bringing new effects under the MXR brand to the market.




The first Distortion+ pedals is the mustard brown box called the "script logo", referring to the "MXR" and "Distortion+" text being in script lettering. The very first ones made during 1973-74 were built into enclosures made by a small company called Bud, thus the oldest (and most collectable) units are the "bud box" versions, which carry the BUD label at the inside of the bottom cover. In 1974 MXR started full-scale production using their own MXR aluminium boxes with their own name "MXR Innovations" on the inside of the bottom plate.
One interesting feature of the script logo units is the additional text on the circuit board, "Hand built by guitar players" which shows that at the beginning the whole effect industry was driven by musicians inspired to building good sounding equipment for their own use, with commercial success not being the sole driver. Well, at least that is what I would like to believe. :)
These units use a LM741CN operational amplifier with a typical large signal gain of around 200 V/mV to drive the cross-coupled germanium clipping diodes.
  MXR Distortion+ Script Logo BMXR Distortion+ Script Logo MXR Distortion+ Script Logo MXR Distortion+ Script Logo Circuit Board MXR Distortion+ Script Logo Circuit Board  


The second version of the Distortion+ was released in the early 80's. The company logo was changed from the script logo to a more modern look, commonly called the block logo, which is still in use today. Also in the interior of the unit many changes can be noticed from the pervious version. The additional comment on the circuit board is removed and many of the components are changed to similar components from other vendors. A first inspection did not reveal any changes in component values, except for the operational amplifier, which has been changed to a UA741CP. The datasheet shows only minor differences between this opamp and the LM741CN, but since already small deviations in the input resistance and capacitance can affect audible differences, it is not a big surprise that the sound of this unit is different from the script logo unit.
  MXR Distortion+ Block Logo BMXR Distortion+ Block Logo MXR Distortion+ Block Logo  


In mid 1981, MXR updated most of their effects pedal and added a 1/8" DC power input jack, and utilized a DPDT footswitch as well as a red LED indicator. The components on the circuit board are mostly the same as in the pre-LED block logo version (UA741CP opamp). Some components seem to be from different manufacturers, although the values are still the same. Soundwise the difference of the two vintage block logo versions are quite small.
  MXR Distortion+ Block Logo BMXR Distortion+ Block Logo MXR Distortion+ Block Logo  


The MXR Commande series was sold 1981-1983, they featured plastic housings and a somewhat flimsy plastic DPDT switch (as opposed to the stomp-switches used in the earlier pedals). The Commande series did not have a Distortion+, but the pedal labelled "Overdrive" was based on the same circuitry, nevertheless with some modifications. The used opamp was a RC4558P and the values of many components are changed. The Overdrive pedal had higher gain compared to the previous units and the bass and mid frequencies were stronger. The higher gain has a small penalty in increased noise at maximum gain settings.
  MXR Commande Series Overdrive BMXR Commande Series Overdrive MXR Commande Series Overdrive  


The MXR 2000 series was sold 1983-1985. The Distortion+ unit of this series differs heavily from the other Distortion+ units made and the amount of electronics inside is about double compared to the other units. Also the DPDT switching has been replaced with electronic switching.
    The basic distorting stage is still similar as in the other units, with a RC4558N opamp in the driver stage. The unit has two outputs, of which one is used for the regular mode, in which the Level-control operates in the conventional way. The other output is used for the second mode, in which the Level-pot controls the amount of distorted signal compared to the clean signal. It is thus a wet/dry blend (similar as in e.g. Voodoo Lab:s Sparkle Drive) offering a whole range of diverse sounds achievable from this unit.
  MXR Distortion+ 2000 Series MXR Distortion 2000 Series  


After Dunlop purchased the rights for the MXR brand in 1987, they reissued a big part of the line of effects MXR had offered before they went out of business. Among the reissued pedals is the Distortion+ M-104, the circuit of which is actually quite close to the original first versions of the Distortion+ pedal. The used operational amplifier is a LM741CN, the same as in the script logo version. Nevertheless, there are differences in the circuitry and the sound of this unit has its own flaviour compared to the older units, with a slightly sharper and raspier high end and increased gain.
  MXR Distortion+ dunlop BMXR Distortion+ dunlop MXR Distortion+ dunlop  

  Rock riff
Effect settings: Output 10 Distortion 5
Blues riff
Effect settings: Output 10 Distortion 5
Lead riff
Effect settings: Output 10 Distortion 10
Clean Samples Sample #1 (Overdrive off) Sample #2 (Overdrive off) Sample #3 (Overdrive off)
Script logo Sample #1 Sample #2 Sample #3
Earlier Block logo Sample #1 Sample #2 Sample #3
Later Block logo Sample #1 Sample #2 Sample #3
(Commande Series)
Sample #1 Sample #2 Sample #3
2000 Series Sample #1 Sample #2 Sample #3
Dunlop reissue Sample #1 Sample #2 Sample #3


The MXR Distortion+ has undisputedly achieved a more or less legendary status during it's more than 30 years history. The sound of the different units vary from generation to generation, although the same fragrance and flavour of tone can be found in all of them. The new Dunlop reissue is surprisingly close to the tonality of the original script logo units, but it fails to deliver the warmth and softness that is captivated in the oldest units, which is especially noticeable at softer drive settings.
The rarity and mojo surrounding the script logo units make it a sought after collectors item, but it also soundwise offers some sweetness and warmth not as readily achievable from the more recent units.

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