CALIBRATION
1) Connect the VCO to the PSU. Let it "heat up" for ~15mins.
2) Set octave switch to 0 and Tune pot somewhere around 12:00
3) Set Octave switch to +2! Connect multimeter to the TP1 and adjust OCTAVE trimpot (bottom one on
the front panel) until you get +5V on TP1! Switch across all octaves and adjust OCTAVE trimpot, until
you have exactly 1V intervals between octaves. Don’t worry, if you can’t adjust it exactly. We’ll come
back to octave interval adjustment later.
4) Connect a tuner to the saw output of the VCO
5) Connect ka keyboard/midi-CV interface that generates 1V/oct CV to the input
6) Play C4 on the keyboard and use TUNE potentiometer on the front panel to adjust tuning so that
tuner shows C4
7) Play C5 on the keyboard and see the tuner reading
8) If the tuner shows something higher that C5 use SCALE tripmot to INCREASE the frequency of the VCO
slightly. If the tuner shows something lower than C5, use SCALE trimpot to DECREASE frequency slightly
9) Play C4 again and use TUNE potentiometer to adjust tuning so tuner shows C4 again.
10) Play C5 and see, what you get. The tuning should be more precize. If it’s not exactly C5, go back to
step 6
11) Once you are happy with C5, check what you get on C6, C7 and C3. You may need to adjust it little
bit more as described on step 6.
12) Now set the frequency to C4 and rotate the OCTAVE switch around several octaves, and check tuner
readings! If switching octaves up, frequency gradually increases octave by octave, turn OCTAVE
trimpot (top right one) slightly clockwise, set frequency to C4, and check readings again. If the
frequency decreases, turn the trimpot counter clockwise. With slight adjustments you should be able
to get precise readings C4, C5, C6, C7 and C3, C2 when rotating the octave switch.
If you succeeded with calibration – congratulations – you have completed the most difficult module of
Erica Synths DIY line! Enjoy!
GUIDE TO ASSEMBLY OF ERICA SYNTHS POLIVOKS-INSPIRED VCO
