Phasor II Guitar Pedal

6-stage optical phase shifter pedal ala the Mu-tron II with extra features

• Fits in a Hammond BB style box
• Classic RATE, DEPTH, and FEEDBACK controls
• Powered by a standard guitar pedal style center-negative 9VDC power supply
• Expression pedal/CV input jack
  • Connect a Moog EP-3 or similar expression pedal with a TRS cable
  • Or inject a Control Voltage in the range [0v, +5v] with a TS cable
  • An internal jumper selects the destination for the modulation
    • LFO DEPTH
    • LFO RATE
    • MANUAL SWEEP

SCHEMATIC

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Calibration

There are three points of calibration via internal trimpots

• EXP PEDAL TRIM

  • Connect a Moog EP-3 or similar expression pedal to the CV-PED jack and power the pedal ON
  • Make sure that any built in attenuators on the expression pedal are turned all the way up
  • With a multimeter set to DC volts measure the TIP of the CV-PED jack relative to ground (there is a convenient place to clip the black lead of the multimeter on the pcb)
  • Sweep the expression pedal all the way forwards, and adjust the EXP PEDAL TRIM trimpot until you measure +5VDC
  • Sweep the expression pedal back and forth and observe that the tip of the CV-PED jack sweeps from 0v to +5v

• DEPTH TRIM

  • This sets the width of the phasor sweep
  • Adjust by ear so that the sweep width is pleasant

• CENTER TRIM

  • This sets the center of the phasor sweep
  • Adjust by ear so that the bottom "turn around" feels good

• The depth and center trims are somewhat interactive, and should be trimmed together iteratively. Try a variety of rate and depth settings while calibrating.

• Note that while there is a light shield covering the photocells, ambient light will slightly change the sweep when the back panel is off

  • Perform calibration in a dim room. It doesn't need to be pitch black, just avoid shining bright lights right onto the guts

There are no wrong or harmful settings, adjust these to taste. If the expression pedal feels better to you with a different voltage across it, go nuts.

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Current consumed from the 9VDC power input

9VDC : 200mA

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Status of the project:

Task	Status
Schematic capture	☑
PCB layout	☑
Test build	☑
Safe to order boards	☑