The Mu-FX Phasor 2X is a phaser pedal that Mu-FX describes as the Modern Vintage Analog refinement of the original Musitronics Mu-Tron Phasor II. It uses the same analog electro-optical phase-shift circuitry as the 1970s original, but adds switchable 4- and 6-stage phasing with independent controls, assignable expression pedal control, and stereo output12.
The pedal is Mu-FX's "Modern Vintage Analog" refinement of the original Musitronics Phasor II pedal1. It is housed in Mu-FX's signature "mini-mu" enclosure with retro graphics1.
Four- and six-stage optical phasing
The Phasor 2X's main addition over the original is a choice of two phasing modes: 4 or 6 stages, selectable from the right-side footswitch3. The 6-stage section is like the original Mu-Tron Phasor II, while the 4-stage section has its own control set13. An adjacent LED shows which mode is active: blue for 6-stage, green for 4-stage1.
The original Phasor II was a six-stage phaser, with six phase-shift stages providing a maximum of 1080 degrees of phase-shift, and a phasing rate range of 1Hz to 18Hz56. Aion FX notes that the Phasor II is essentially one-half of a Bi-Phase, with a nearly identical LFO and phase-shift topology7. The current Musitronics reissue of the Phasor II also lets you externally select between 4 and 6 stages of optical phasing5.
Mu-FX's own sound samples for the Phasor 2X were recorded with a Fender Stratocaster (Custom Shop '54 pickups) in the bridge/middle position, running directly into the pedal and out into an Otis Trudeau amplifier1.
The controls
Each phasing mode has its own control set, and the PHASE STAGE footswitch switches between the 6- and 4-stage sections and their respective knobs1.
| Control | What it does |
|---|---|
| RATE (6 Stage) | Controls the speed of the LFO wave that controls the effect |
| DEPTH (4 Stage) | Controls the range of the phase sweep |
| FEEDBACK (4 Stage) | Sets the amount of effected signal fed back into the effect for a more pronounced effect |
| FX BYPASS footswitch | Engages the effect or true bypasses it (active bypass can be selected internally) |
| PHASE STAGE footswitch | Switches between 6 and 4 stages of phasing and their control sets |
Both footswitches are silent, using relay switching of the audio, with multi-color LEDs for FX/bypass and phase stage selection12. Pedal of the Day found that the three simple controls "are anything but, giving you more phase-infused tonal opportunities and options than you can ever imagine"3.
Power and connections: 12V AC
The Phasor 2X runs on a 12V AC power supply, and the maker warns: "DO NOT use with a DC supply." A standard 9V DC pedal supply, or a daisy chain built for DC pedals, will not work1.
Mu-FX says the 12V AC supply is used for optimal headroom and hi-fidelity sound1. The supply is included in the price when sold in the USA, but sold separately elsewhere24. This differs from the current Musitronics Phasor II reissue, which runs on 9V DC5.
Connections are straightforward: a standard ¼" input jack accepts any instrument or audio input, OUT 1 is the main mono output, and OUT 2 sends a second signal that makes the pedal stereo when used with OUT 1, or can be used alone for a varied phase effect1. Premier Guitar described OUT 2 as a stereo, modified 5-stage output2.
Expression and CV control
The EXP PEDAL jack is a standard ¼" TRS input that accepts an expression pedal or control voltage for manual control of specific functions1. Premier Guitar described it as an EXP/CV (T-R-S) input for expression pedal or synth CV effect control2.
The EXP MODE toggle switch sets what the expression pedal controls1:
- (O): Turns off expression pedal control of any function
- (EXP <): Sets the expression pedal to control the RATE function
According to Premier Guitar, the EXP toggle switches control rate or sweep functions, and with no EXP/CV pedal plugged in they allow the Phasor 2X to act as a stereo "multi-pole-filter" EQ2. Mu-FX's own "Leslie Phase" sample uses the 4-stage section with the MU-XP2 expression pedal set to control the RATE function1. For comparison, the Musitronics Mu-Tron Phasor III lets you assign CV to rate, depth or none8.
What reviewers said
Pedal of the Day reviewed the pedal in July 2017 and was positive across the board, saying it provides "more functionality, options and user-friendliness across the board" than the original, and that the effects Mu-FX puts out are "truly inspirational, to say the least"3.
"all fears were whisked away in a matter of about 3 seconds when we first hit that Bypass switch and unleashed the sonic beauty held within this retro-designed effect."
Delicious Audio covered the pedal in August 2017 and pointed readers to a demo video by Gear Man Dude9.
Videos
Premier Guitar
gearmanndude
Pedal of the Day
Questions
Can I power the Phasor 2X with a 9V pedal supply?
No. The Phasor 2X runs on a 12V AC power supply, which Mu-FX says gives optimal headroom and hi-fidelity sound, and the maker explicitly warns not to use a DC supply. A standard 9V DC pedal supply will not work. The 12V AC supply is included with USA orders and sold separately elsewhere.
Is the Mu-FX Phasor 2X true bypass?
Yes, by default. The FX BYPASS footswitch engages the effect or puts it in true bypass, using silent relay switching of the audio. An active bypass mode can be selected internally instead, via an internal switch, if you prefer to keep the circuit in the signal path.
Is the Phasor 2X stereo?
Yes. OUT 1 is the main mono output, and OUT 2 sends a second signal that makes the pedal stereo when used together with OUT 1. OUT 2 can also be used on its own for a varied phase effect. Premier Guitar described the second output as a stereo, modified 5-stage output.
Who designed the Mu-FX Phasor 2X?
The Phasor 2X was designed by Mike Beigel, co-founder of Musitronics, the company behind the original Mu-Tron Phasor II in the 1970s. The pedal is sold under the Mu-FX name, which Pedal of the Day described as the newly revamped Mu-FX operation.
How does the Phasor 2X differ from the original Phasor II?
It keeps the same analog electro-optical phase-shift circuitry but adds switchable 4- and 6-stage phasing with independent controls, stereo output, assignable expression pedal control, and true bypass with silent relay switching. The original Phasor II was a six-stage phaser with three controls and no stereo output.
Sources (9)
- Mu-FX Phasor 2X, Musitronics Mu-Tron
- Mu-FX Releases the Phasor 2X, Premier Guitar, 2017-05-31
- Mu-FX Phasor 2X Optical Phaser Effects Pedal Review, Pedal of the Day, 2017-07-17
- Mu-FX revisits its multi-stage stereo phaser with the Phasor 2X, gearnews.com, 2017-06-01
- Phasor II, Musitronics Mu-Tron
- Mu-Tron Phasor II, Musitronics Mu-Tron (mu-tron.com)
- Hexatron Optical Phaser / Mu-tron Phasor II, Aion FX, 2026-07-03
- Phasor III Vintage Silver, Musitronics Mu-Tron
- Mu-Fx PHASOR 2x Phaser, Delicious Audio, 2017-08-18
