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  9. Erica Synths POLIVOKS-INSPIRED VCO User manual

Erica Synths POLIVOKS-INSPIRED VCO User manual

GUIDE TO ASSEMBLY OF ERICA SYNTHS POLIVOKS-INSPIRED VCO
If you are reading this, most probably, you are about to build Erica
Synths DIY Polivoks-inspired Oscillator. This VCO is 35mm deep,
skiff friendly, has solid mechanical construction and doesn’t require
wiring. The core of the VCO is borrowed from famous Russian synth
Polivoks VCO and in exponential converter we use the original
matched transistor IC that was used in Polivoks. But we significantly
updated schematics:
1) we introduced +-10V regulators for greater stability of operation,
2) we adjusted signal amplitudes to match requirements of
contemporary modular synths and made all output signals available
simultaneously,
3) we redesigned CV inputs to accept positive CV signals,
4) we introduced PWM circuit with manual and voltage controlled
pulse width,
5) we introduced synchronization input, so you can sync the VCO to
other VCOs.
The Oscillator kit comes in three versions:
1) Set of 2 PCBs + matched transistor IC + mechanical parts (PCB
connectors and spacer) + 5 position rotary switch,
2) Set of 2 PCBs + matched transistor IC + mechanical parts (PCB
connectors and spacer) + 5 position rotary switch + panel,
3) Full kit.
FEATURES:
•Triangle, saw and pulse wave outputs
•Manually adjustable and CV controlled pulse width
•Great tracking across 8 octaves
•Exponential FM input with attenuator
•Synchronization input
•Octave switch –5 octaves
•Skiff-friendly design
SPECIFICATIONS:
•Audio output amplitude 10Vptp
•Octave range C0 –C8
•Panel width 12HP
•Module depth 35mm
•Power consumption 34mA@+12V, 36mA@-12V
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3
4
2
5
6 7 8 9
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8
The TUNE knob allows you to set the tune of
the VCO across two octaves
Use Octave switch to set octave the VCO tune
octaves up or down instantly
Adjust pulse width manually!
This is FM CV attenuator
These are VCO outputs. All three waves are
available simultaneously
Patch 1V/oct CV source here. The VCO tracks
well across 8 octaves
Patch FM CV source here for vibrato effects!
This is VCO Sync input. Patch another VCO
output here to reset VCO circle. This gives you
new, interesting waveforms
9Patch PWM CV source here! 10Vptp CV signal
affects pulse width form 1% to 99%
Take precautions with regard to electrostatic discharge (ESD) safety. Handling components should be done
in electrostatically safe environment. Use personal and workplace grounding. Any discharge (even a minor
one) from body to a component may permanently damage it.
Our PCBs have silkscreened both component values and designators nevertheless we highly recommend
you to print out files with component placement before you start assembly of the module. And, please, at
least take a look on this manual!
Some components are marked as NU (not used) –leave those unpopulated! Some components are market
as OPTION (those are for optional modifications) –leave those unpopulated for now.
ASSEMBLY
1Solder horizontally placed resistors and diodes on both PCBs (Controls board and Main board)! Pay attention on
orientation of diodes!
2Solder IC sockets and vertically placed resitors on the Main board, ferrite beads on the Control board and
capacitors of both boards!
GUIDE TO ASSEMBLY OF ERICA SYNTHS POLIVOKS-INSPIRED VCO
Controls board
Main board
3Solder electrolytic capacitors, transistors and
trimpots on the Main board! Mind polarity of
electrolytic capacitors and orientation of
transistors! Don’t mix up NPN and PNP transistors!
5Place 16x16mm textolite piece under the
switch (it will ensure that the switch is the
same height as potentiometers) and solder the
switch, potentiometers, two multiturn
trimpots and jacks! Cut off orientation stopper
on the switch.
GUIDE TO ASSEMBLY OF ERICA SYNTHS POLIVOKS-INSPIRED VCO
4Turn the Main board around and
solder 1x8 male connectors!
6Turn the connectors PCB around and solder
voltage regulators, resettable fuses and
electrolytic capacitors! Also solder 1x8 female
connectors and PSU connector! Bend
resettable fuses down.
Negative lug of
electrolytic
capacitor is marked
with a stripe!
7Now it’s time to make some
measurements! Connect a PSU to controls
PCB and measure, if you get +-12V and +-
10V on the connector to the main PCB
(refer to schematics)! If you are not getting
these voltages, check, if you have soldered
10V regulators correctly!
9Connect both PCBs together! And fix the bottom one
with the M3x6 screw! For all our modules with 2
PCBs white stripes on both PCBs have to match.
10 Install the front panel and potentiometer knobs!
8Use M3x6 screw to install 11mm header on the
controls PCB!
GUIDE TO ASSEMBLY OF ERICA SYNTHS POLIVOKS-INSPIRED VCO
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

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