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2MoreF

Calibration of CEM/AS3320 dual analog filter eurorack-modul.

Preconditions

Required or recommended tools are:

  • 440Hz tone-reference (tuning-fork, fork oscillator etc.).
  • Voltage meter.
  • Frequency meter (if available).
  • Eurorack for power (+12V/-12V) and keyboard-CV.
  • 16pin Eurorack cable for modul-connection to the rack-bus.
  • patchcables for modular synthesizers.

Calibration

Table of Contents

Board_B silk topside
Board_B silk topside overview

Offset-Adjustment for left(1) and right(2) side

Offset-adjustment is done with precision trimmers 'P1' and 'P3' on board B.
All following setups are done with Modul topside-potis at left and right side.

  • Set 'Frequency'-potentiometers 'P4'(1) and 'P9'(2) to 12 o'clock position.
  • Set 'Res.' (resonance)-potentiometers to value:10 ('CW', self oscillation).
  • Set 'Mod' (modulation)-potentiometers to 12 o'clock position (0 := no modulation).
  • Set all other potentiometers to CCW position.
  • connect 16pin eurorack cable from rack-bus to the socket K1 Pin1 on board B. Be carefull to fit the allignment of buspower Pin1 (-12V) .
  • connect patchcables between signal-output 'OUT(1)' ot 'OUT(2)' and audio-out (or frequency meter, if available).
  • power up the eurorack.
  • Turn precision trimmer 'P1' | 'P3' on 2MoreF board B until the soundable- or measured- frequency is close as possible to 440Hz.

1V/Oct.-Adjustment for left(1) and right(2) side

The CV-range (1V/octave) must be tuned with potentiometer 'P2' | 'P4' on board B after the offset-adjustment .
The 'Res.' (resonance)-potentiometer must be set to value:10 ('CW', self oscillation).
The following setups are done with Modul topside-potis and generating CV-voltages.

  • Set the keyboard-CV for playing key-note A4.
  • Set 'Track'-potentiometer to full CW.
  • Turn 'Frequency'-potentiometers CCW until the soundable- or measured- frequency is again 440Hz.
  • play key-note A3 and check the measured frequency. If the measurement is above 220Hz, then turn 'P2' | 'P4'-potentiometer 'CCW', else 'CW'.
  • play key-note A5 and check the measured frequency. If the measurement is above 880Hz, then turn 'P2' | 'P4' -potentiometer 'CCW', else 'CW'.

Repeat this adjustments until the measuared frequencies are A2=110Hz, A3=220Hz, A4=440Hz and A5=880Hz.
Repeat also the 'offset-adjustment to fit the 440Hz to 12 o'clock position on 'Frequency'-potentiometers.

Final check

Voltage measurements on Testpoint: TP1 and TP2.

The 'Res.' (resonance)-potentiometers must be set to value:10 ('CW', self oscillation).
Set all other potentiometers to CCW position.

  • connect voltage-meter between GND and TP1 or TP2.

The following table shows the measured voltages depending on the 'Frequency'-potentiometer position.

Poti-position Frequency (Hz) measured voltage on TP1 or TP2 (mVolt)
min (CCW) less then 20 Hz 175 mVolt
12 o'clock 440 Hz 84 mVolt
max (CW) above 20 kHz -47 mVolt

License

Hardware:cc by-nc-sa 4.0