Hero VCO module, 100x200 mm, with six knobs, one slide switch, four trim pots, and ten jacks

The Analog Output Hero VCO is a 3340 based voltage controlled oscillator synth module. Notable features of the Hero include:

  • Triangle, ramp, pulse, and sine waveforms with separate output jacks.
  • Uniform, zero-centered ±5 Vpp output amplitudes for the various wave shapes.
  • Input jacks for two V/oct CVs, as well as PWM, linear FM, and exponential FM (pitch) CVs with attenuators.
  • Separate initial pulse width and PWM attenuator knobs.
  • Wide pulse width range.
  • Switch selectable hard, soft, or no sync.
  • 11 position octave switch plus fine tuning knob.
  • Front panel access to trimmers for calibration of V/oct tracking, center pitch, and pulse width range limit.
  • Entirely through hole construction with readily available components.

Two well known problems with the 3340 in its datasheet configuration are addressed:

  • Regulated -5 V supply improves stability and suppresses pulse width frequency shift.
  • Falling edge oscillations on pulse wave shape are eliminated.

But perhaps the most significant feature of the design is the link header. This may be used to connect the Hero to one or more of its sister module, the Sidekick VCO , in a modern riff on the classic Moog 921a/921b system. The Sidekick is half the width of the Hero and lacks some of the Hero’s front panel controls and inputs, but internally is essentially the same circuit as the Hero. Via the link, the Sidekicks receive summed V/oct pitch CV, linear FM CV, and pulse width CV from the Hero, based on its front panel controls and inputs. In this way a common set of control voltages is presented to the Hero and all its Sidekicks. The link also permits the Sidekicks to be hard or soft synced to the Hero. This allows easy configuration of a multi-oscillator synth voice in a relatively compact system.

Git repo