Mu-Tron Phasor II – The world’s best phaser pedal

By | April 4, 2021


Once you have acquired a new musical gadget, it is good to also acquire something that can change its tone. My choice when it comes to distorting, polluting or beautifying sounds is often a phaser, a type of power device that appeared about 40 years ago.

The actual effect could be achieved even before the 70s, but then two tape recorders were needed and the approach was complicated and time consuming. When the phaser pedal came as a guitar effect in the early 70’s, it quickly became popular.

mutron_.thumb.png.9e09c666df38d8ff327bd53703e940ad.pngThis is how the phase works
In short, a phaser works as follows: A sound is divided into two equal parts, one part of which is allowed to pass a number of filter steps. These filters pass the signal unaffected, except that it is phase shifted for each filter step it passes. The phase shift depends on the frequency of the signal. After the filters, the two signals are mixed together again. When the unaffected signal is added to the phase-shifted one, certain frequencies will be out of phase and attenuated sharply – so-called comb filter effect.

In 1975, Musitronics released the pedal we will now take a closer look at: the Mu-tron Phasor II. In addition to being the most beautiful phaser pedal, it is also the best. It is simply difficult to end up wrong with this gold nugget in the signal chain. The silver-shining Phasor II has the following knobs: rate, depth and feedback. Rate controls the speed of the sweep, depth how large the sweep should be and feedback how much of the signal should be fed back. The technology used, opto-switch, was actually obsolete as early as 1974, when big brother Bi-phase (Mutron Bi-phase is two Phasor II in one and the same pedal) was released. But as the technology was less accurate than the modern bold technology, it gave a more musical expression and therefore quickly became popular.

Magical ability
I would like to say that all the settings on this pedal sound good. It has a, for lack of better words, magical ability to spice up a dull string sound and make it sit in the mix. Something that is important to me when I record is to make things happen on a subtle level. With Feedback and Depth set to a low value, you can, as it were, change the feeling of the sound, so that it changes without the listener noticing that something is happening – perfect on accompaniment guitar or bass and drums.

Phasor II is the best pedal when it comes to handling the lower frequencies. Other phaser pedals kind of add a sound, while this one instead mixes up the basic sound and the effect and creates a completely new sound.

A phaser can be used to create leslie-like effects. Here, however, the Mu-tron does not fit as well if you compare with, for example, Roland’s Phase Five. Phase II is more “disco”. Try driving thin tracks that wander through feedback circuits and opto-switches. The sound is soft and beautiful.

Another interesting trick to get mind-expanding sounds is to use, for example, a Farfisa Compact from the 60’s (I’m not really a fan of the 60’s but some good things actually appeared) and drive it through a Phasor II. Because you can cover a very wide frequency range with Farfi san, the phasersound becomes huge and as well as hypnotic. This is widely used by bands such as Spacemen 3, Spiritualized and Spectrum. Entire songs can be based on sweeps from Phasor II (or Bi-phase).

These bands are not the only ones who have realized the greatness of Musitronic’s fantastic phase effects. Ladytron (who released Mu-tron EP in 2002), Daft Punk and Stereolab are other examples of creative musicians who use the products. Lee “Scratch” Perry got an early demo version of Bi-Phase and it came to color a large part of his music production.


Type: Phaser pedal
Manufacturer: Musitronics Corps
Year of manufacture: 1975
Used price: From about SEK 2,800 and up

This is an updated and revised article, previously published in Studio no. 5-2011