MXR Phase 90
MXR · 1974
What It Is
The MXR Phase 90 is a four-stage phase shifter introduced in 1974. It has a single Speed knob and operates at 9V. It was made famous by Eddie Van Halen, who used it extensively on Van Halen I and II. Several versions exist: the original Script logo version (transistor-based, smoother and warmer), the Block logo version (op-amp-based, brighter and more aggressive), and the EVH Phase 90 (script-style circuit in EVH livery). The Headrush model labeled 'Orange Phase 90' refers to the original Script-style version, which is generally considered the more musical of the two.
Tonal Character
Smooth, musical phase shifting with a warm, slow sweep at low speed settings and a more dramatic effect as speed increases. The Script version has a slightly warmer, less aggressive phasing character than the Block version. At low speeds it adds subtle movement to clean tones. At higher speeds it becomes a more pronounced 'whoosh' effect. Unlike a flanger, phasing doesn't cancel frequencies as dramatically — the effect is smoother and more musical.
Found In
HeadRush
| Model Name | Controls | Notes |
|---|---|---|
| Orange Phaser | Speed | The standard Phase 90 model — smooth, musical phase shifting based on the original Script-logo circuit. Warmer and less aggressive than the Block logo version. The Speed control is the only adjustment. This is the primary Phase 90 model for most applications. |
| Square-Phase | Speed | A second Phase 90-inspired model with a different waveshape driving the phase modulation — produces a more abrupt, rhythmic phase sweep compared to the smooth sine-wave sweep of the Orange Phaser. The effect is more pronounced and choppy at equivalent Speed settings. Useful when you want the phase effect to be more rhythmically obvious or when a more dramatic sweep suits the part. |
Videos
Manual
View ManualFamous Uses
- →Eddie Van Halen — Van Halen I and II (defining use) — Van Halen (1978)
- →Jimmy Page — Led Zeppelin (various studio use)
- →David Gilmour — Pink Floyd
Best For
Controls Explained
Descriptions reflect the real-world gear these models are inspired by. Your modeler's implementation may vary. Use as a starting point — always trust your ears.
Speed
The single control on the Phase 90 governs the rate of the phase modulation cycle. At minimum (fully counterclockwise), the sweep is extremely slow — barely perceptible movement that adds subtle animation to sustained notes and chords. Around 9 o'clock, the sweep rate produces the classic 'slow phase' quality — a gentle, rolling movement that enhances clean and light-overdrive tones without being distracting. The 10 o'clock to noon range is where most classic Phase 90 applications live — medium speed that adds clear movement and the characteristic whooshing sweep. Above noon, the phase becomes more pronounced and faster, producing the more dramatic phase effects. At maximum, the speed is fast enough to produce a tremolo-like quality on some amp combinations. For Eddie Van Halen's characteristic Phase 90 sound, medium speed with moderate to high gain is the target — the phasing interacts with the amp's distortion to create a three-dimensional, swirling quality to the lead tone.
Sample Configurations
Starting points for common tones — dial in from here.
| Name | Speed | Notes |
|---|---|---|
| Subtle Movement | 2 (9 o'clock) | Very slow sweep. Gentle animation to clean tones without being obvious. |
| Classic Rock Phase | 5 (noon) | The EVH setting zone. Medium speed with overdrive produces the signature Van Halen swirl. |
| Fast Flutter | 8 (3 o'clock) | Fast sweep for dramatic phase effect on single sustained notes. |