doepfer-a-110-4

Doepfer A-110 VCO

Four-waveform analog VCO with PWM and hard sync

8 HP Eurorack module

The Doepfer A-110-4 is a Thru-Zero Quadrature VCO that outputs pure sine and cosine waveforms simultaneously. Unlike most VCOs that derive sine waves from sawtooth via waveshaping, the A-110-4 uses a true sine/cosine oscillator core, producing exceptionally clean waveforms with minimal distortion. The "thru-zero" capability means the oscillator can pass through zero frequency and continue in reverse, enabling FM synthesis spectra impossible with conventional VCOs. It features both exponential (XTune, 1V/Oct, XFM) and linear (LFrq, LFM) frequency control sections. The linear section is key to thru-zero operation: sweeping LFrq through center causes the waveform to decelerate, stop, and reverse direction. Output level is approximately 10Vpp. Width: 8HP, current: +90mA/−30mA.

Features

  • Four simultaneous waveform outputs: sawtooth, square, triangle, sine
  • Frequency range of approximately ten octaves
  • Hard Sync input for locking slave VCO to master VCO
  • Two CV inputs (CV1 and CV2) summed for pitch control, following 1V/octave standard
  • CV1 normalled to internal System Bus for keyboard tracking without patch cables
  • CV2 with attenuator knob for FM depth control
  • Manual Pulse Width control for square wave shaping
  • Two PWM voltage control inputs (PW CV1 and PW CV2) summed, PW CV2 level adjustable via attenuator
  • Range switch with five octave/footage positions
  • Fine tuning Tune knob with approximately plus/minus half octave range
  • Exponential FM response
  • Warm-up time of approximately 20 minutes for full tuning stability

Controls & Jacks (10)

  • XTune
  • XFM Amount
  • LFrq
  • LFM Amount
  • 1V/Oct In
  • XFM CV In
  • TZ Control LED
  • LFM CV In
  • Sine Out
  • Cosine Out

How-To Guides

  • Basic VCO Keyboard Tracking Setup
  • LFO Pulse Width Modulation
  • LFO Frequency Modulation Vibrato
  • Hard Sync Timbral Sweeping
  • Two-Oscillator Detuned Chorus
  • Audio-Rate FM Bell and Metal Tones
  • Sub-Octave Layering with Divider
  • Soft Flute or Vibraphone Tone
  • VCO Sync Tone Colour Morphing

Explore the interactive A-110 VCO panel on BleepDex — tap any control to learn what it does.

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