The MXR Deep Phase is a compact phaser pedal from MXR, introduced in October 2021 as the M279. It is based on the classic Phase 90 circuit, squeezed into MXR's mini housing, with two controls: a Speed knob and a Mode II switch that doubles the number of phasing stages1. MXR describes the sound as "crystal clear with a pronounced swoosh, scooped midrange, and a dynamic, voice-like response to your attack"2.
The pedal is now out of production. MXR lists it as a legacy product, so what is on shelves is remaining stock and the used market2.
What it does to your sound
A phaser splits your signal, shifts one copy's phase across a range of frequencies, and recombines the two, producing the moving notches that players hear as a "swoosh." The Deep Phase runs four phase shifter stages by default, which MXR calls a smooth effect; the Mode II switch doubles that to eight stages for what MXR describes as twice the number of peaks and a more animated texture2. Delicious Audio's write-up characterized the stock mode as the smoother sounding of the two5.
Where the Deep Phase differs from the vintage circuit it is built on is level. MXR says the original suffered a serious volume drop when engaged, and that the Deep Phase was carefully designed to match the player's level instead2. For players who have fought that drop on older four-stage phasers, that is the practical difference.
The controls: Speed and Mode II
The control set is deliberately minimal, in the tradition of MXR's one-knob phasers, with one added switch.
| Control | What it does |
|---|---|
| SPEED knob | Adjusts the effect rate, from slow sweeps to fast swirl3 |
| MODE II switch | Push to the IN position to engage 8 phase shifter stages instead of the default 4, for a more pronounced and textured effect3 |
| Footswitch | Toggles the effect on and off; a blue LED indicates when it is on3 |
The manual gives the internal LFO (the oscillator that drives the sweep) a range of 0.15 to 50 Hz, so the Speed knob spans very slow, barely-moving sweeps up to fast, choppy phasing3. Premier Guitar summarized the Mode II switch as toggling "between a smooth and highly textured effect"6, and Gearnews described it as taking the 4-stage phase shift and doubling it into an 8-stage phaser7.
Power and connections
Setup is a standard two-cable affair: an instrument cable from your guitar to the M279's INSTRUMENT jack, and another from the AMPLIFIER jack to your amp's input3.
The Deep Phase cannot be powered by a battery. It requires the Dunlop ECB003 9-volt adapter or an MXR Brick Series power supply2. At 18 mA it is light on a power brick's budget, but there is no battery fallback if your supply dies mid-gig3.
With true bypass switching, the pedal passes your signal unbuffered when off3.
Where it came from
MXR launched the Deep Phase in early October 2021, adding a compact two-knob phaser to a lineup that already included the Phase 90 and the mini Phase 95. MusicRadar reported it as building on the Phase 90 circuit in a mini format1, and Guitar World's Michael Astley-Brown framed the launch as MXR chasing classic Small Stone phaser territory in a mini enclosure8. It carried a $129.99 street price at launch4; Gearnews later listed it at $111.00 at Thomann in December 20217.
What reviewers said
Coverage at launch was positive and focused on the format. Gearnews, rounding up the best effect pedals of 2021, called the Deep Phase's Mode II switch out as the feature that takes the 4-stage phase shift and doubles it, and concluded that "then this compact new pedal is certainly one to check out" for fans of phasing effects7. Delicious Audio's Paolo De Gregorio walked through the two modes, noting the stock 4-stage mode as the smoother sounding option against the doubled 8-stage setting52.
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Questions
Is the MXR Deep Phase discontinued?
Yes. MXR lists the Deep Phase as a legacy product that is no longer in production. It was launched in October 2021 with a $129.99 street price, and remaining stock may still be found on the used and clearance market, but it is not part of the current MXR lineup.
Can the MXR Deep Phase run on a battery?
No. Both the MXR product page and the M279 manual state plainly that the pedal cannot be powered by a battery. It needs the Dunlop ECB003 9-volt adapter or an MXR Brick Series power supply, drawing 18 mA at 9 volts DC.
Is the MXR Deep Phase true bypass?
Yes. The M279 manual lists the bypass type as True Bypass, so with the effect switched off the signal passes through without active buffering. The footswitch toggles the effect on and off, with a blue LED indicating when it is engaged.
Does the MXR Deep Phase have a volume drop?
No. MXR says the original vintage circuit suffered a serious volume drop when engaged, and that the Deep Phase was carefully designed to match the player's level instead. That level-matched engagement is one of the pedal's selling points over the older design.
What does the Mode II switch do on the MXR Deep Phase?
By default the Deep Phase runs four phase shifter stages for a smooth effect. Pushing the Mode II mini-switch to its IN position engages eight stages, which MXR describes as delivering twice the number of peaks and a more animated, textured phasing sound.
Sources (8)
- Has MXR perfected the mini phaser pedal with the Deep Phase?, MusicRadar, 2021-10-04
- MXR® DEEP PHASE™, Jim Dunlop (jimdunlop.com)
- M279.pdf, Jim Dunlop, 2021
- MXR launches the Deep Phase, a new compact two-knob phaser, Guitar.com, 2021-10-04
- MXR Deep Phase M279, Delicious Audio, 2022-08-25
- MXR Unveils the Deep Phase, Premier Guitar, 2021-10-01
- Best Effect Pedals 2021: Did your favourite make our Top 10?, Gearnews (www.gearnews.com), 2021-12-26
- Is MXR's new Deep Phase mini pedal taking on classic Small Stone phaser tones?, Guitar World, 2021-10-04
