Prophecysound Systems Pi-Phase Mk2

The return of the long-lost king of phasers

Back in the 1970s a small yet innovative company called Musictronics built what many still consider to be the finest phase shifter ever built - the Mu-Tron Bi-Phase; a unit that could be referred to as a "pedal" in only the most liberal sense of the word - it was very large and actually best suited to stand or tabletop use, and it included satellite footswitches that attached to the main unit. In spite of its monster size, it had a sound and features that very few pedals before or since could even began to rival. Unfortunately Musictronics / Mu-Tron was sold to ARP on a royalty basis in the late 1970s and ARP went out of business shortly after that, and in the years since the demise of Musictronics the prices for used Bi-Phase units have gone through the roof. Today you can easily drop two grand or more on one in decent shape - assuming you can find one. Fortunately, the good folks down under at Prophecysound Systems decided to take on the considerable challenge of trying to reverse engineer and bring this long-lost classic back. How did they do? Read on to find out.  

What You Need To Know

• The Pi-Phase Mk2 is a carefully researched and exceptionally well built pedal that is designed to replicate the sound and features of the legendary 1970s era Musictronics Bi-Phase dual phase shifter. The Pi-Phase, while smaller, has the same controls and a similar top panel layout as a Bi-Phase, making it easy to use for those who are familiar with the originals. The graphics separate each unit and its functions into different areas, so it's easy to tell what everything is and what it controls.

   

• Housed in a much smaller and more pedalboard-friendly unit than the original, the Pi-Phase measures approximately 2" H x 7.4" W x 4.8" D and weights about 1.65 pounds. This makes it considerably smaller and lighter than the pedal it is based on. The case is metal and painted white, and the top and rear panels feature cool blue, black and white Lexan panels. The control labels are high contrast and very easy to read.

   

• Each phasor has its own individual 1/4" input and output jack, which are mounted on the rear panel. As with the vintage unit the Pi-Phase is based on, these are mounted "backwards" from what you'll find on most pedals today, with the inputs on the left and outputs on the right side of the pedal (when viewed from the player's perspective). This makes wiring the pedal into your board a bit trickier, but you'll most likely want to have it placed in a location on your board that allows for easy repatching whenever you want - that way, you you retain more flexibility than you'd have if you hardwired it in such a way that repatching would be difficult without taking the whole board apart.

• You'll also find the jacks for an optional external CV / expression pedal, and the power jack located on the rear panel.

• Like the original, the Pi-Phase combines two phase shifter units (named "Phasor A" and "Phasor B") into a single housing. Each Phasor has its own Feedback and Depth controls, as well as individual red LEDs to indicate when either one (or both) are active, and individual footswitches for turning each phasor on and off. Switching is true bypass.

   

• The two Phasors are each equipped with their own Sweep Generator controls. Phasor A's Sweep Generator has a control for setting the Rate of the LFO and phase sweep, as well as two toggle switches - one to allow you to select between Sine Wave or Square Wave modulation, and a second that allows you to select between the Rate control or an optional external CV / expression pedal for controlling the sweep.

   

• Prophecysound Systems recommends using an expression pedal with a 10k linear pot. Examples include the Roland EV-5 and EV-7 as well as the Dunlop DV3 volume / expression pedal. I tested the review unit with a EV-5, and it worked perfectly.  

   

• Phasor B's Sweep Generator also has the Rate control, as well as a Sine / Square Wave switch, but you have even more options - a dedicated knob allows Phasor B to source its sweep from Generator 1 or 2, or the optional external pedal. A switch labeled Sync allows you to toggle between normal and reverse. This allows you to invert Phasor B's modulation relative to Phasor A, even when both are using the same sweep source.

   

• That's not all! Phasor B has a dedicated Input control that allows you to select between the rear panel Input A, Input B or the output from Phasor A. Yup - that means that the Pi-Phase can do phase shifting in parallel or series.

   

• Internally, the construction quality is first rate, and while you'll notice numerous trim pots inside, the manufacturer strongly cautions you not to go mucking around in there. Each pedal is carefully calibrated at the factory and it is easy to mess that up if you don't know exactly what you're doing.

• No power supply is included with the pedal, and battery powering it isn't an option, so you will need to source your own supply. Prophecysound will help by providing the information about exactly what you need, and may even be able to tell you who sells them in your area, but they decided not to provide power supplies since 1) they're heavy and would add to the cost of shipping the unit from Australia and 2) because stocking them for a variety of countries really doesn't make tons of sense when people can get them locally anyway.

   

• So what exactly do you need to power the Pi-Phase? A 15V AC (NOT DC!) adapter that can supply a minimum of 500mA, and that is equipped with a 2.1mm plug.

   

• Need a power supply in the USA? The good folks at Analogman can assist you. Just tell them you're looking for a supply for a Pi-Phase.

   

• Need some suggestions for setting to get you started? Recreations of the original's preset "cards" are included, as well as an extra one with an original Prophecysound Systems preset, as well as a couple of blank cards for saving your own favorite settings.

Limitations

• Unlike the originals, the preset cards that are included are not designed as "overlays" that can sit on the unit's top face. Still, the inclusion of the cards is yet another thoughtful touch.

   

• Like the originals, the input and output jack configuration is "reversed" from what most pedals today use, with the input on the left and the outputs on the right.

   

• People who wanted an exact clone in all respects may be somewhat disappointed by the unit's different physical size and slightly different layout. The more sensible among us will probably think they should get over it - go buy a vintage original if that's the only thing that will satisfy you. For the rest of us, this unit is far more useable and practical than the original, especially if you want to use it live, or put it on your pedalboard.

   

Conclusions

How does it sound? In a word, glorious! And in stereo, it's almost indescribably good. Of course you don't have to run it in stereo to dig what this pedal has to offer; series phase shifting is cool too, and there is tons of flexibility here that you may not fully grasp until you try the various options for yourself. Dig super-slow phasing? This can do it, as well as lots of other cool single phaser sounds and mesmerizing dual phaser combinations. Check out the sound clips below for just a few examples of what this beast is capable of. Between this and their other highly regarded phase shifter (the Prophecysound Systems Infinitphase MkII), Prophecysound Systems are definitely in the running for the title of reigning champs when it comes to this specific type of effect.

While the Pi-Phase isn't an original design or concept, it's an extremely well researched and executed take on a true and long-discontinued classic. Does it sound exactly like a vintage Bi-Phase? It's close enough that I seriously doubt you'd be able to consistently and accurately tell the difference between the two in a side by side double-blind listening test. Some might quibble about it not maintaining the same huge physical size as the pedal that inspired it, but the vast majority of players will appreciate its more manageable dimensions. While it's smaller than a Bi-Phase, nothing feels cramped and it's a very easy pedal to use in spite of the wealth of possibilities it has. It's also cool that the footswitches are built-in and you don't have to worry about connecting (or losing) a separate footswitch unit. And for expressive control, the ability to use currently-manufactured expression pedals that are widely-available is another plus. Best of all, compared to the cost of a Bi-Phase, the Pi-Phase is a bargain, and far more affordable. If you're a guitarist, keyboardist or studio owner that is into the sound of phasing, give this pedal a try. If you're like me, you may decide it's just about the coolest phase shifter still being manufactured today. I did. I'll be purchasing one at my first opportunity for my own guitar rig, and for use in the studio.

Resources

Prophecysound Systems Pi-Phase Mk2 (599 AUD ex GST, approximately $427.84 US dollars at the time of this writing, available direct from Prophecysound Systems - power supply and shipping are extra)

Prophecysound Systems product web page

Sound Samples:

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Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines.