Phase 90

A phaser splits your signal, shifts the phase of one copy, and mixes them back together. Where the two copies cancel, you get notches, little gaps in the sound. Sweep those notches up and down and you get the whoosh, like a jet going over or water swirling down a drain.

The Phase 90 does it in four stages, which gives two moving notches. The one knob, Speed, sets how fast they move. No depth, no feedback, no mix. Slow, it’s a gentle wash. Fast, it’s a wobble.

So you set the speed once, with your hand, and from then on the pedal is just on or off. There’s nothing to fiddle with in the middle of a song, and nothing to get wrong.

What people noticed was how mellow it was. A lot of phasers sound like something laid on top of the guitar. This one sounds like part of the guitar, moving.

Eddie Van Halen used it all over the first Van Halen album, in 1978: “Eruption,” “Atomic Punk,” “Ain’t Talkin’ ’bout Love.” It turns up again later on “Everybody Wants Some!!” and “Drop Dead Legs.”

What he liked was how subtle it was next to other phasers. That sounds like an odd thing to want from a man who played that loud, but it was the whole trick. When a solo came, he kicked it on, and the guitar stood out in the mix without sounding like it had put on a costume.

Put on “Eruption” and listen past the notes to the tone itself. The movement inside it, the swirl under all those notes, is the Phase 90.

David Gilmour used one on Pink Floyd’s “Shine On You Crazy Diamond” in 1975. Mick Jones put it on the Clash’s “Lost in the Supermarket” in 1979. Jimmy Page used one.

Matt Bellamy went further and had it built right into his custom Manson guitars, which is one way to make sure you never leave it at home.

The early MXR pedals had the name in script. Around 1976 or 1977 (the dates don’t agree), the line switched to block letters in a black box. For a while the parts got mixed, so you can find script cases holding later circuits and the other way around. Purists will tell you nothing but an original script-logo Phase 90 will do.

Those early ones were spare in other ways too. Until 1981, MXR pedals had no LED to tell you they were on, no jack for a power adapter, and no true bypass. A battery, one knob, and a footswitch.

The Phase 90 opened the door for the rest of the line. The Distortion+, the Dyna Comp, and the Blue Box came after it. The Phase 45 arrived at the end of 1974, and the Phase 100 in 1975.

MXR went out of business in 1984. Dunlop bought the brand in 1987 and has reissued the Phase 90 in several forms since, plus an Eddie Van Halen signature model. Keith Barr went on to found Alesis.

In 2019, Tom Morello’s pedalboard was the same one he’d used since the early ’90s, and there was a Phase 90 on it, next to a Cry Baby, a Whammy, and Boss delays. Nobody keeps a pedal on the floor for the better part of thirty years because of its features.

Same box, same single knob, and “Eruption” doesn’t sound like “Shine On You Crazy Diamond,” which doesn’t sound like “Lost in the Supermarket.” The difference was never in the pedal. It was in the person standing on it.