SYNTH-VCO-01

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SYNTH-VCO-01 REV1 FRONT 3D.png

Features

  • Build of Pico VCO by HAGIWO
  • Digital Voltage Controlled Oscillator (VCO)
  • Three modes: Wavefold, FM and AM
  • PWM output with 2 pole low pass filter
  • Each mode has eight built-in waveforms
  • XIAO RP2040 CPU
  • (5) Pushbuttons
    • Octave Up/Down
    • Mode Up/Down (Wavefold, FM and AM)
    • Push Timbre switches between 8 waveforms
  • (2) Knobs
    • Freq fine adjust
    • Mod adjust
  • Standard EuroRack 16 pin header
    • Supports 12V in with on-board 5V regulator
    • 5V regulator can be not installed if 5V is available on EuroRack connection
  • Card is not a Eurorack card
    • Probably too deep, needs cabling
  • (4) 6-32 mounting holes

XIAO RP2040 Pins

  • Pin 1, GP26 = Vol/Oct, Analog In
  • Pin 2, GP27 = Freq Pot, Analog In
  • Pin 3, GP28 = Mod, Analog In
  • Pin 4, GP29 = Mod Pot, Analog In
  • Pin 5, GP6 = Timbre Pushbutton, select waveform type, Digital Input
  • Pin 6, GP7 = Gate (optional), Digital Input
  • Pin 8, GP1 = Octave Down, Digital Input
  • Pin 9, GP2 = Audio Output, PWM out
  • Pin 10, GP4 = Mode Down, Digital Input
  • Pin 11, GP3 = Mode Up, Digital Input
  • Pin 12 = +3.3V
  • Pin 13 = GND
  • Pin 14 = +5V

Software

Videos

Checkout/Testing

  • Nice sine wave
  • Very little noise

VCO-01 sine.png

FREQ_CV MOD_CV MOD_POT FREQ_POT MODE_SW OCT_SW MEASURE (Hz) SIG TYPE
0 1.61 CCW CENTER CENTER CENTER 261.4 SINE MIDDLE C
0 0 CCW CCW CENTER CENTER 70.5 SINE
0 0 CCW CW CENTER CENTER 107.9 SINE
0 0 CCW CCW UP CENTER 66 WAVEY-SAW
0 0 CCW CCW UP CENTER 70.5 SAW
0 0 CCW CCW CENTER DOWN 35.4 SINE
0 0 CCW CCW CENTER UP 141.6 SINE
0 0 CCW CCW CENTER CENTER 70.5 SINE
1 0 CCW CCW CENTER CENTER 142.9 SINE
2 0 CCW CCW CENTER CENTER 293.4 SINE
3 0 CCW CCW CENTER CENTER 598.4 SINE
4 0 CCW CCW CENTER CENTER 1200 SINE
5 0 CCW CCW CENTER CENTER 2441 SINE

Issues

Rev 1

  • Working/no functional issues
  • Mode/Oct switches s/b 3 way toggle with center off
  • R13 s/s has 330K, s/b 33K
  • R14 s/s has 220K, s/b 22K
  • C6 s/s hard to see
  • OpAmp U2 uses wrong schematic symbol
    • ADD WIRE U2-1 TO U2-6 (VOUT) ON REAR
    • ADD WIRE U2-7 TO U2-5 (VCC) ON REAR
    • LIFT IC U2-2
    • LIFT IC U2-4
    • ADD WIRE IC U2-2 TO SOCKET U2-4
    • ADD WIRE IC U2-4 TO SOCKET U2-2
  • Works with rework

Assembly Sheet