MXR Phase 90

MXR Phase 90 The Phase 90 is a compact effects pedal produced by MXR that became a staple in popular music for its distinctive phasing sound. Widely used on electric guitar and bass guitar, it has appeared on recordings and performances associated with artists, venues, and studios across rock, blues, funk, and progressive genres. The pedal’s simple interface and characteristic circuitry made it influential among cottage builders, boutique manufacturers, and session players working with labels and producers worldwide.

History

Introduced by MXR during the 1970s, the Phase 90 emerged amid developments in stompbox culture driven by manufacturers like Electro-Harmonix, Boss, Dunlop Manufacturing, and Vox seeking compact, roadworthy units for touring acts. The pedal circulated through scenes centered in cities such as Los Angeles, New York City, London, and Nashville and was adopted by session musicians in studios like Sun Studio, Abbey Road Studios, and Electric Lady Studios. Throughout eras of analogue effects evolution alongside companies like Fender, Gibson, and Marshall Amplification, the Phase 90 maintained presence on bills at festivals including Glastonbury Festival, Woodstock, and Monterey Pop Festival via artists and road crews. Its design lineage reflects influences from earlier modulation devices used by artists associated with labels such as Columbia Records, Atlantic Records, and Warner Bros. Records.

Design and Electronics

The unit uses an analogue phase-shifting circuit employing operational amplifiers and phase-shift networks similar to designs used in vintage equipment by firms such as Moog Music, Roland, and Korg. Key electronic elements include a low-frequency oscillator (LFO), RC networks, and transistor stages inspired by components common to units produced by National Semiconductor suppliers and manufacturing partners in Japan and United States. Early iterations relied on point-to-point wiring and through-hole components comparable to contemporaneous products from Sherman, Mu-tron, and Farfisa. The pedal’s single control—Speed—manipulates the LFO rate to sweep multiple all-pass filters that create the characteristic notches in the frequency response used by players working with rigs from Mesa/Boogie, Ampeg, and Peavey. Power options evolved from internal batteries to external DC adaptors promoted by Boss specifications and boutique suppliers.

Variants and Models

MXR released multiple variants and cosmetic runs, with collector interest similar to vintage circuits from Fender, Gibson, and boutique builders such as Analog Man and Electro-Harmonix. Notable MXR-era variants include early orange-box editions, black-box reissues, and limited runs timed with anniversaries promoted by retailers like Sam Ash Music Stores and Guitar Center. Competing or derivative models by manufacturers such as Dunlop, EHX, and boutique labels incorporated additional features—stereo outputs, depth controls, and true-bypass switching—echoing innovations seen in units from Strymon, Eventide, and TC Electronic. Collectors compare serial-numbered batches with vintage units from Ampeg and aftermarket casings produced by small shops in Portland, Oregon and Los Angeles.

Sound and Usage

The Phase 90 produces a warm, sweeping phase effect used on records and stages by players in bands associated with Van Halen, Pink Floyd, King Crimson, The Rolling Stones, Led Zeppelin, and The Who. It colors lead tones, rhythm comping, and ambient textures in genres performed at venues like Royal Albert Hall, Madison Square Garden, and Red Rocks Amphitheatre. Players integrate the pedal with amplifier heads by Marshall or Fender and speaker cabinets from Celestion and Jensen to shape tone, or place it in amplifier effects loops preferred by producers affiliated with Rick Rubin, Brian Eno, and George Martin. Session engineers working at Capitol Studios, Sunset Sound, and Compass Records facilities have used it on guitar, synth, and keyboard tracks for artists signed to Island Records, RCA Records, and Polydor Records.

Modifications and Repairs

Modders and technicians from communities linked to suppliers such as Mouser Electronics, Digi-Key Electronics, and repair shops near Nashville and Austin, Texas perform component swaps: replacing 4558 op-amps with modern equivalents, adding depth or feedback controls, and fitting true-bypass switching inspired by designs from Electro-Harmonix and Boss. Repair practices draw on service manuals and schematics like those used for vintage gear from Fender, Vox, and Hiwatt, and consider parts from manufacturers such as Vishay and Panasonic. Boutique builders and artists associated with Adrian Belew and David Gilmour have commissioned custom mods—LED indicators, buffered bypass, and stereo phasing—often documented in magazines such as Guitar Player, Premier Guitar, and Sound on Sound.

Notable Users and Recordings

Prominent users include Eddie Van Halen (noted for work on albums released by Warner Bros. Records), David Gilmour (Pink Floyd catalogues under Harvest Records and Columbia Records), and Adrian Belew (King Crimson recordings through EG Records). The unit appears on landmark recordings and live albums tracked at studios like Abbey Road Studios and mixed by engineers who have worked with The Beatles, Led Zeppelin, and Queen. It has been part of touring rigs for acts that played major events such as Live Aid, Monterey Pop Festival, and Isle of Wight Festival, contributing to tones on records distributed by Island Records, Atlantic Records, and EMI Records. Category:Effects pedals