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Apex JFET Phaser

Based On
MXR® Phase 45
Effect Type
Build Difficulty
Project Summary
A simplified two-stage version of the classic Phase 90, using matched JFETs to produce a swept phase effect.
Apex JFET Phaser printed circuit board

Printed Circuit Board

What's included?
PCB only. Build instructions and parts list can be viewed or downloaded from this page.


In stock

Complete Kit

Not yet available.
Kits are developed based on interest, so if you’d like to see one for this project, let us know.
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Project overview

The Apex JFET Phaser is based on the MXR Phase 45, a short-lived “little brother” to the MXR Phase 90 that was released in 1975, the next year after the more famous circuit.

The Phase 45 design is very similar to the Phase 90, but as the name implies, there are only half of the phase stages, two instead of four. While it was certainly cheaper to produce than the Phase 90, and that was probably the motivation for its release, it does have a milder character of its own that many people prefer to the original.

In 2017, MXR released a mini pedal called the Phase 95 that has a switch to activate a Phase 45 mode by bypassing two of the phase stages. We considered combining the 45 and 90 into one project in a similar way, but if you compare the schematics, there are enough differences between the two circuits that a single switch can’t cover both with 100% accuracy to the original circuits.

The phase stages themselves are constructed differently, particularly the extra components around the JFETs, and the Phase 90 also includes an active transistor stage that mixes the dry and wet signals differently at the output.

The Apex is a direct copy of the Phase 45 circuit, with two added modifications. A Depth control allows the intensity to be dialed back, a modification that we also added to our version of the Phase 90. And by using a toggle switch to change the phase-frequency capacitors to a 10:1 ratio, it gives a warbly phase-shift sound that’s more reminiscent of a Univibe.