MXR phase 90

Home Forums Products Rackmount MXR phase 90

  • This topic is empty.
Viewing 4 reply threads
  • Author
    • #106104

      I'm trying to find the phaser preset that most closely emulates the legendary MXR phase 90 script logo circa 1974-1977. I own a re-issue of the physical unit, but I'd rather have it "inside" the Eventide so I can include in more elaborate settings.
      Unfortunately, I can't find a single preset from my H7600 that sounds like it. It's a mono pedal, with low frequency swoosh, and mostly affects the higher frequencies.
      I found an interview on the web from the MXR engineer who worked on the re-issue MXR phase 90. Help appreciated in either how to tweak an existing preset, or how to VSig a new one.

      "The heart of a Phase 90 is the all-pass filter circuit, which shifts the phase of its input signal by a certain amount of degrees, depending on signal frequency and resistive/capacitive components. The Phase 90 achieves its unique sound by summing the output of a four-section all-pass filter with the input signal. This produces signal cancellations or nulls at frequencies where the two signals are of opposite phase.
      In the Phase 90, the four-section all-pass filter produces two nulls ? at 180 degrees and again at 540 degrees. Then, by controlling the resistive portion of the all-pass filter with a low frequency oscillator, the two null points are moved up and down the audio spectrum, producing the moving Phase 90 effect."

    • #118374

       Hard to say what really goes on inside the old pedal!

      Usually there are two ways you can build a replica: either you have the original and know how to do "surgery" on it to get all the guts secrets of it…or using your ears is the simple way to go. Path #1 is the best.

      I'm only guessing what you may try here, in Vsig.

      The PhaseShift gives you a choice of poles #, from 2 to 50. These are the all pass filters.

      You may try using 2 Phase modules w/2 (or 4 poles) each, connecting them in series. Use an LFO thru a MIX module (as in the TC 1210 preset) or thru a SCALE module (as in the 3_D Phase Inverter preset) to create phase inversion, before connecting it to the PhasShift MOD input.

      You may also try having a 2 ch. mixer before the phase shift to create feedback…helps THAT woosh a lot. Experiment placingthe 2PhaseShift in series OR in parallel, or having 2 in series processed by 2 in parallel or the opposite of it. Try using more poles in each module. Then summ all Phasers thru a mono mixer. You have to try it all to make your ears realize what the sound is.

      Also try using some filters to cut out some low end before the phasers….

      There's a lot you can try.

      have fun


    • #118536

      Here's an attempt I made at reproducing a standard Phase 90. Very similar to what was described above – I found that I got the sound closer after I put in the low-pass filter on the feedback loop. Sounds pretty close when A/B-ing the pedal, but I'm sure there is room for improvement.


      HEADM adc 2 2 mix1-out mix1-out "MXR Phase90" "" 4 menu1-obj menu2-obj menupage-obj info-obj ;=0,0,80,0
      KNOB hyst "hysteresis: %0.1f dB" "" 0 20 0.01 9 ;=91,462,80,0
      KNOB dec "decay : %1.3f sec" decay 0 9 0.001 0.1 ;=91,294,80,0
      KNOB att "attack: %5.3f sec" attack 0 10 0.001 0.002 ;=91,210,80,0
      KNOB thr "thresh: %0.1f dB" thresh -100 0 0.1 -30 ;=91,378,80,0
      MENUPAGE menupage "noise gate" gate 4 thr-obj att-obj dec-obj hyst-obj ;=807,396,80,0
      TEXTBLOCK info 1 "Emulation of the MXR Phase 90 Phaser" ;=1016,241,80,0
      MENUPAGE menu1 "phaser params" phaser 4 rate-obj depth-obj fb-obj mix-obj ;=805,220,80,0
      MENUPAGE menu2 advanced advanced 2 shape-obj "lowpass trim-obj" ;=804,314,80,0
      SKNOB3 rate "rate :%7.2f Hz" "" 0 0.01 0.4902 rate-out 0 100 0 ;=325,104,80,0
      TEXTKNOB shape "shape : %s" "" 8 6 sine triangle square peak "warp sin" "warp tri" "half sine" "half peak" ;=325,204,80,0
      KNOB "lowpass trim" "lowpass: %0.0f" lowpass 0 20000 1 2500 ;=382,528,80,0
      PERCENTKNOB fb "feedback: %3.0f %%" "" -100 100 1 50 ;=325,288,80,0
      PERCENTKNOB depth "depth : %3.0f %%" "" 0 100 1 80 ;=616,147,80,0
      PERCENTKNOB mix "mix :%4.0f %%" "" 0 100 1 50 ;=798,136,80,0
      C_SUBTRACT sub 1 mix-out ;=897,63,80,0
      Show More...

      GATE gate add-out att-out dec-out thr-out hyst-out 0.1 ;=217,44,80,0
      HIGHCUT highcut phaser-out "lowpass trim-out" ;=560,526,80,0
      ADD add adc-in1 adc-in2 ;=85,36,80,0
      LFO lfo adc-null rate-out 0 shape-out 0.5 0 ;=486,148,80,0
      MIX feedback gate-out highcut-out 1 fb-out ;=485,54,80,0
      PHASESHIFT phaser 4 feedback-out lfo-out depth-out ;=715,47,80,0
      MIX mix1 gate-out phaser-out sub-out mix-out ;=1014,14,80,0
      TAIL zazula

      Show Less...
    • #118574

       You could definitely put this on my wish list for future H8000 upgrades in the vintage effects category. I know it's hard work, but maybe some day? 


    • #129712

      Anyone willing to send me his/her MXR P90 for this?

      Only way I can try to make it happen, IF possible.



Viewing 4 reply threads
  • You must be logged in to reply to this topic.