Modcan VCDO 58B Voltage Controlled Digital Oscillator

motm-101Quantity: 1From the Modcan B website:

The VCDO 58B represents a new breed of sound generation for the modular environment. The primary design goal was to implement a variety of digital synthesis techniques and to combine them together in one module

The most significant wave-shaping feature of the 58B utilizes the technique referred to as Two-Operator FM, providing a wide variety of timbres from mellow bell like tones to complex distortion.

The inclusion of harmonically rich sample based wave tables extends the complexity of the FM effect comparable to multi-operator systems. AM (Amplitude Modulation) is also available on-board as is standard Exponential FM using the Expo FM Jack Conventional analogue VCOs are modulated with externally generated signals from LFOs and secondary VCOs etc. Digital implementation of the VCDO 58B affords superior FM stability with internally generated, phase locked, sine table modulator. The FM Index function controls the amplitude or depth of the modulation while the Ratio control tunes the modulator to a rational frequency value relative to the carrier frequency. Phase locking the modulator with the carrier produces beat-free timbres that retain spectral relationships over the entire frequency range. The 58B includes standard VCO wave forms and adds several sample based wave tables. Pulse width modulation and hard sync are also supported. Switch selectable quantized pitch tracking in semi-tone steps or non-quantized continuous frequency control with fine tune.Firmware by DSP designer Eric Brombaugh.


  • 32-bit NCO – 50 micro-Hertz resolution (no zippering)
  • Phase-locked FM/PM gives beat-free modulation
  • 32 real-time voltage controlled modulation/carrier ratios
  • Fractional modulation/carrier ratios for complex sub-harmonics
  • Modulation index range from 0 to 314% for a wide range of continuously varying wave shapes.
  • Real-time voltage-controlled modulation index for subtle wave shaping
  • 32-bit pseudo-random noise generator – won’t repeat for 119 hours at highest frequency setting; longer at lower frequencies.
  • Voltage controlled selection of 16 wave forms
  • Quadrature secondary output at 90 degrees out of phase
  • Amplitude and Pulse width Modulation AM/PWM
  • Switch selectable quantized 1V/Oct input
  • Audio and LFO range frequency
  • Voltage controlled FM Index and modulation Ratio
  • Crystal tuning stability with +/-0.005% pitch tracking accuracy over 18 octaves


  • Sine
  • Triangle
  • Saw
  • Square w/PWM
  • Double Pulse w/PWM
  • Random Stepped (with CV controlled variable interpolation)
  • 10 sample based wave tables


  • Frequency Range: 18 Octaves
  • High 10Hz-10kHz
  • Low .040Hz-40Hz
  • Output: +/-2.5V pk-pk @1Kohms
  • Input CV 0-5V @100Kohms


  • Changed knobs to MOTM-style
  • Bruce Duncan-provided power supply connection for off-board +5V

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