MXR, also known as MXR Innovations, was a manufacturer of guitar effects units, founded in 1973 by Keith Barr (who went on to found
Alesis) and Terry Sherwood (who went on to co-found Applied Research & Technology). MXR was based in the United States in Rochester,
New York. MXR Innovations, Inc. was incorporated in 1974. The MXR trademark is now owned by Jim Dunlop, which continues to produce the
original effects units along with new additions to the line.
Founded in 1973, MXR Innovations entered the effects market as a pioneer with the development of tough and rugged stomp boxes, simple
utilitarian designs, and small sizes. Jim Dunlop, having purchased the brand in 1987, continues MXR's traditional pedal line of
original MXR classics that have come to define the brand, such as the Phase 90 and Dyna Comp, as well as modern classics like the
Carbon Copy and Fullbore Metal. Dunlop has also added a line dedicated to bass effects boxes, MXR Bass Innovations, which has
recently released the Bass Octave Deluxe and Bass Envelope Filter, both pedals winning Editor Awards in Bass Player Magazine,
and Platinum Awards from Guitar World Magazine. The MXR Custom Shop is responsible for recreations of vintage models such as the
hand-wired Phase 45, as well as doing limited runs of pedals featuring premium components and highly modified designs such as the
new Custom Comp.
The first MXR effects pedal was the M-101 MXR Phase 90. A milder version of the effect was also released, the MXR Phase 45, and a
programmable version, the Phase 100. A 9 volt battery was used to powered these effects and could give them up to 500 hours of power.
The input was directly connected to the circuit's power supply. Like many other pedals of the day, MXR pedals (prior to 1981) did not
have LED's, A/C adaptor jacks, or true bypass switching. Over the years, there were two distinct periods that the reference series
pedals went through.