MXR ZW90 Zach Wylde Phase

The MXR ZW90 Zach Wylde Phase is a signature phaser pedal made by MXR and designed in collaboration with guitarist Zakk Wylde. It is an analog pedal, and RockBoard's PedalPedia describes it as delivering everything from slow, warm sweeps to more intense, rapid modulation effects, built to add dimension, texture and dynamic movement to guitar tones, with bass and keys also mentioned, in the rock and metal genres Wylde is associated with¹.

What the ZW90 does

The ZW90 is a phaser: it sweeps a series of notches through your signal to produce the swirling, jet-like modulation players use for everything from a slow shimmer behind a riff to a fast, urgent warble. MXR's product description says the pedal provides classic analog phaser modulation, with the sweep speed set by the Rate knob, and a rugged stompbox design suitable for live and studio use¹.

Because it is a signature take on the Phase 90, the circuit it descends from matters. The Phase 90 is a four-stage phaser, meaning four phase-shifting stages in series, and it also includes an active transistor stage that mixes the dry and wet signals differently at the output, which shapes how pronounced the effect sits against your clean tone³. MusicRadar, in a piece on the pedal's heritage, called the Phase 90 "still the benchmark for classic swirl"⁴.

The controls: a single Rate knob

The ZW90 keeps the one-knob layout that defined the original. Its panel is short enough to list in full¹⁵²:

MusicRadar's review rounds out the panel: "a standalone Speed dial, basic input/output and an industry-standard footswitch"². There is no depth, feedback or mode switch to set, which is the point of this style of phaser: one dial, one sound family, from subtle to swooshing.

A Phase 90 variant made with Zakk Wylde

MusicRadar's review frames the pedal plainly: "the big man drops his spin on the MXR Phase 90"². The original Phase 90, model M101, is described by its maker, Dunlop, as taking you "from subtle, spatial shimmer to all-out high velocity swooshing with the twist of a knob"⁶. When MXR revisited its history, the company noted that "this four-stage phaser featured a single knob to control the rate of the effect," the same control layout the ZW90 carries⁵¹.

MXR has made many Phase 90 variants over the years. The ones named alongside the ZW90 in the site's phaser coverage include:

• EVH Phase 90, the signature model for Eddie Van Halen
• '74 Vintage Phase 90, a reissue-style take on the early circuit
• Phase 95, a compact model combining two Phase 90 and Phase 45 styles

The ZW90 sits in that line as Wylde's version. MusicRadar's overall verdict was that there is "no need to upgrade" if you already have a simulation of the Phase 90 or a decent phaser in general², a useful benchmark if you are weighing it against what is already on your board. For the wider field, see the site's Phaser Pedals page.

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