The MXR M101 Phase 90 is a phaser pedal made by MXR, a company now under Dunlop Manufacturing, Inc. It is a single-knob effect: turn the SPEED knob to set how fast the phase sweep moves, and step on the footswitch to switch the effect on or off, with a red LED showing when it is on. MXR's manual describes what it does to a signal in plain terms: "Add's shimmery velocity to lead licks and a thick swoosh to chords"1.
The controls
The Phase 90 keeps things deliberately simple. There is one knob and one switch, and nothing else to set1.
| Control | What it does |
|---|---|
| SPEED | Controls overall effect rate |
| FOOTSWITCH | Toggles effect on/bypass (red LED indicates on) |
That single-control layout is the template a large family of MXR phasers grew from, including the Phase 45, the Phase 100, the Script Phase 90, the EVH Phase 90 and the 50th Anniversary Phase 90. Players who want more knobs in a similar footprint can look at the Deep Phase, which adds Speed and Feedback controls and four- and eight-stage modes, or the Phase 95, which combines Phase 45 and Phase 90 circuits in a mini pedal.
Power and specifications
The M101 runs on 9 volts DC and draws 5 mA, which is a very light load for a pedalboard power supply. It can run from one 9-volt battery (remove the bottom plate to install it) or from a 9-volt adapter such as the Dunlop ECB003/ECB003EU or a DC Brick power supply1. The manual lists a 1 MΩ input impedance, a 10 kΩ output impedance, and nominal input and output levels of -20 dBV1.
On bypass, the two available accounts differ. The Dunlop manual lists the bypass type as "True Hardwire"1, while a GuitarPCB technical analysis states "Not true bypass comes with a LED and AC adapter."2.
The bypass type is described differently by the maker and by an independent technical analysis, so players who care about true bypass in a long chain may want to hear the pedal in their own setup before deciding where it sits.
Using it with other instruments
Dunlop's manual says the pedal "Works well with bass, keyboards and even vocals"1, so it is not a guitar-only effect. The high 1 MΩ input impedance and low 5 mA draw also make it an easy addition to a board shared with a bass rig. For more on the effect type itself, see the site's guide to Phaser Pedals.
Price and availability
Guitar Pedal X reported a list price of $100 for the plain M101 Phase 90 as of 5 October 2023, noting that "while the plainer MXR M101 Phase 90 is $20 less at $100"3. MXR has since marked the model's history with limited editions, including the gold M101GLD 50th Anniversary Edition Phase 90.
Videos
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Questions
Does the MXR Phase 90 take a battery?
Yes. According to the Dunlop manual, the MXR Phase 90 is powered by one 9-volt battery, and you remove the bottom plate to install it. It can also run from a 9-volt DC adapter such as the Dunlop ECB003/ECB003EU or a DC Brick power supply, which is convenient for pedalboard use.
Is the MXR M101 Phase 90 true bypass?
The Dunlop manual lists the bypass as True Hardwire1. A GuitarPCB technical analysis describes the pedal as not true bypass, noting it comes with a LED and AC adapter2. If bypass character matters to your setup, it is worth hearing the pedal in your own chain.
What power supply does the MXR Phase 90 need?
The manual specifies a 9-volt DC supply, such as a Dunlop ECB003/ECB003EU adapter or a DC Brick power supply. A 9-volt battery also works. With a current draw of only 5 mA, the pedal is light on any power supply.
Can I use the Phase 90 with bass?
Yes. Dunlop's manual states the pedal works well with bass, keyboards and even vocals, so it is not limited to guitar. Its 1 MΩ input impedance and 5 mA current draw also make it an easy fit on a mixed pedalboard.
How much current does the Phase 90 draw?
The Dunlop manual lists the current draw at 5 mA, which is very low by pedal standards and means the Phase 90 puts minimal demand on a battery or DC power supply.
What is the input impedance of the Phase 90?
The manual lists a 1 MΩ input impedance and a 10 kΩ output impedance, with nominal input and output levels of -20 dBV.
Sources (3)
- M101.pdf, Dunlop Manufacturing, Inc., 2019
- MXR Phase 90 Analysis, GuitarPCB
- Guitar Pedal X, Guitar Pedal X, 2023-10-05
