M101 Phase 90

MXR Phase-90 Phaser. This is the one-knob phaser that has, for all practical purposes, dominated all other phasers that have come before, or since...

Thermionic Studios owns four (4) Phase 90 pedals available for rental:

• Two (2) CSP101SL "Script" Phase 90s,
• One (1) EVH-90 Edition Phase 90, and,
• One (1) EVH-90 SE 35th Anniversary Phase 90

IRONY: Despite making the article about the standard "block" Phase 90 phaser, we don't have any standard MXR Block Phase 90 phaser pedals. We have nothing against the standard block phasers, we just don't think they sound AS GOOD as the older script-logo architecture model; we don't think they offer the best sounds - we believe musicians are more partial to the sounds of the script logo pedal.

If you're attached to the block pedal sound, it's possible to use an EVH-Phase 90 with the "script" button not pressed in.

If you're interested in renting one of our Phase-90s, please don't hesitate to contact us.

Controls

M101 Image from Jim Dunlop

• Knob 1 - "Speed": Turning the knob clockwise increases the speed of sweep across the phasing effect
• Footswitch 1 - "On/Off": This switch toggles the pedal between Active and Bypass modes.

Bypass: Buffered

All versions of the Phase-90 - whether by the original MXR company, or from later Dunlop/MXR, have a buffered signal bypass. There is no exception.

General Information

Unlike the other versions of the M101, the "Block" Phase 90 has a tough textured coating. It maintains the historic orange color that MXR used when they first released (their first product!) the original bud-box script-Phase 90.

Of all the versions of the Phase-90 that are available, the block Phase-90 has the most pronounced phasing effect present in the affected signal. The script-logo Phase-90 has been re-issued by Dunlop, and we believe it's more subtle phase-shifting effect sounds better, or perhaps could better be described as "more musical".

Most "gearheads" tend to like effects or amplifiers with lots of knobs or other controls. The irony is the perennial popularity of the Phase-90 and its single knob control. We're of the opinion that the Phase-90 remains popular for a few reasons:

1. It sounds really good
2. It's tough
3. A single knob makes it easy to control while playing

Script Phase 90

CSP101SL from Jim Dunlop

This version of the Phase-90 is easily distinguishable from the "block" version in that it has a smooth orange coating on the enclosure and displays the classic script logo.

There are a couple of different versions of the Dunlop/MXR "Custom Shop Script" Phase-90:

1. A handwired version of the original "script" logo Phase 90 (CSP-026). This version is true to the original with:
   • No external AC power supply jack
   • No LED indicator to indicate active/bypass status
2. A standard-built "script" logo Phase 90 (CSP101SL) that includes AC power jack and LED indicator.

The handwired (CSP-026) version is harder to get a hold of, and isn't displayed on the Dunlop website, making it more "apocryphal". However, there are music stores that have it available for sale.

We own two (2) copies of the "standard-built" (CSP101SL) pedal. We think the AC power jack and LED indicator are helpful to musicians.

EVH Phase 90

EVH-90 from Jim Dunlop

Dunlop started making this version of the Phase-90 several years ago, specifically for Eddie Van Halen, as a custom edition of the pedal. It is easily identified as it carries the trademark red-with-white-and-black stripes of EVH.

The LED differs on this version. It is blue instead of red.

We have one (1) copy of this Phase-90. We were able to get a good deal on it and thought it would be cool to pair with our EVH117 EVH Flanger 35th Anniversary version since they would be matchy-matchy.

The Script Button

This version of the Phase-90 is different from the standard MXR Phase-90 because it comes with a "script" button. The script button is in the upper-left corner of the pedal. This button toggles between the original "block" version phaser effect, and, when depressed, the subtler "script" version phase effect.

EVH SE Phase 90

"EVH-90 SE" from Stratcat.biz

The EVH90SE is exactly the same pedal as the EVH90 version of the Phase 90. It's only real difference is the black-on-white motif of early Eddie Van Halen on the pedal enclosure. It is functionally no different. Despite our protestations of "don't get signature gear", we got this because we were able to get a good deal on it, and because we thought it would be cool and fun to pair with our EVH117 EVH Flanger that also shares the black-on-white style motif.

• Being exactly the same model, except for the different paint job, the Eddie Van Halen 35th Anniversary version also has the "script" button. It functions in exactly the same manner.

Pedal Manuals

• MXR "Script" Phase-90 Manual
• MXR Standard EVH Phase-90 Manual
• MXR EVH 35th Anniversary Phase-90 Manual

Phase Inversion:Yes/No

Schematic ID	Electronic Part	Action	Phase State
IC1	RC4558	X	X
Q1	2N5952	X	X
IC2	RC4558	X	X
Q2	2N5952	X	X
IC3	RC4558	X	X
Q3	2N5952	X	X
IC4	RC4558	X	X
Q4	2N5952	X	X
IC5	RC4558	X	X
Q5	2N4125	X	X
IC6	RC4558	X	X

Schematic

We happened to find this schematic for the Phase-90. It's interesting in that it offers some alterations that, if you were to build your own Phase-90 from scratch, that you could implement for additional versatility:

• A Phase 90 / Phase 45 toggle switch
• Another toggle switch to enable an unusual "univibe" effect
• An additional "Depth" knob to set the depth or shallowness of the phase swell

We can't speak as to how well these modifications would work if you were implement them. We're currently not interested in attempting them on our own pedals since there's no room in the enclosure for an additional depth knob.

Phase 90 Schematic by Nero Rox, unaware of any Copyright claims.

Artists

• Eddie Van Halen
• Josh Homme
• Billie Joe Armstrong
• Dave Grohl
• Steve Vai
• Jimmy Page
• Slash
• David Gilmour
• JD Cronise
• Paul Gilbert
• Marty Friedman
• Andreas Kisser
• James Iha
• Tom Morello
• Melissa Auf der Maur
• George Lynch
• Michael Amott
• Matt Pike

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Additional Sources

• https://www.electrosmash.com/mxr-phase90
• https://puzzlesounds.com/blog/history-mxr-phase-90-effect-pedal/
• https://equipboard.com/items/mxr-m101-phase-90--4