MXR Phase 45
Two-stage JFET phaser — subtler, sweeter cousin of the Phase 90.
We don't ship reference schematics until they've been hand-authored against authoritative sources (manufacturer service docs, ElectroSmash analyses, GEOFEX writeups) and reviewed in the simulator. Until then, the BOM, signal chain, controls and mod notes below are accurate, and you can still add this pedal to a project — it just won't include a circuit yet.
About
A simpler version of the Phase 90 using only two matched JFET all-pass stages instead of four. The result is a single, gentler comb-filter notch sweep — less obvious than the Phase 90 but more transparent and chord-friendly. The same triangle-LFO drives the JFET gates.
Signal chain preview
5 stagesQuick facts
- Released alongside the Phase 90 in 1975; the 45 was marketed as the 'subtle' option.
- Reissued in 2014 with the original script logo and through-hole layout.
- Two-stage phasers give one notch; four-stage (Phase 90) gives two; six-stage (Phase 100) gives three.
Controls
- Speed (LFO rate)
Mod recipes Pro
3 mods- Depth control
Add the depth knob the stock pedal lacks.
How: Replace the LFO's output coupling resistor with a 100k linear pot — wiper feeds the JFET gates. Full CCW = no modulation.
- Resonance / feedback
Sharper, more vocal notch.
How: Route the output of stage 2 back to the input of stage 1 through a 100k linear pot in series with a 10 nF cap.
- Four-stage upgrade
Turn it into a Phase 90.
How: Add two more matched JFET all-pass stages between the existing two. Re-trim bias to keep all four matched within 5%.