The Electro-Harmonix XO Stereo Polyphase is a phaser pedal from the company's XO line. Electro-Harmonix describes it as a pedal that can "Generate seductive stereo phase shifting at its finest," built around stereo outputs that let the phase sweeps move across the left and right channels rather than sitting in a single mono path1.
What it does
As a phaser, the Stereo Polyphase sweeps filters through your signal to produce the moving, whooshing effect players use on clean rhythm parts, leads and everything between. What sets this version apart from a mono phaser is the stereo output stage: Electro-Harmonix says players can "Experience cascading sweeps and gorgeous, panoramic imaging through stereo outputs," meaning the effect spreads across a two-amp or stereo rig instead of collapsing to one channel1.
"Generate seductive stereo phase shifting at its finest."
Availability and condition
The XO Stereo Polyphase is not a pedal you will find new on a dealer shelf today. A distributor listing dated October 2026 showed the pedal as sold out, and the example offered was B-stock: the listing described it plainly, "PEDAL SHOWS SIGNS OF USE AND VELCRO ON BACK (see photos). BOX SHOWS SIGNS OF USE." The listed regular price was £153.00 GBP, given in pounds sterling as stated by the seller1.
The unit offered was B-stock, with visible signs of use and velcro on the back of the enclosure. Anyone comparing this pedal against a new purchase should weigh that condition.
If you are shopping for an Electro-Harmonix phaser that is easier to find, the company's Small Stone line is the better-known route: see the Small Stone, the Nano Small Stone or the Stereo Polyphase itself.
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Questions
Is the Electro-Harmonix XO Stereo Polyphase still in production?
The XO Stereo Polyphase is no longer a current catalog item. A distributor listing for the pedal as of October 2026 showed it as sold out, and the unit offered there was described as B-stock, showing signs of use with velcro on the back and a box showing signs of wear. Players looking for a current Electro-Harmonix phaser can look at the Small Stone family instead.
Sources (1)
- EHX XO Stereo Polyphase phaser, Godlyke Distributing, Inc.
