K3020 Dual VCO

K3020 // Dual VCO

Eurorack Dual Voltage Controlled Oscillator - 36HP

The K3200 Dual VCO is a state-of-the-art dual analog voltage controlled oscillator that is both musically and technically superb. The design is optimized for great sound and playability for both tonal and experimental music. Both channels also function as excellent LFOs capable of generating interesting modulating voltages. Dual independent power supplies provide clean power separately to each channel for improved stability. Each VCO core is comprised of a monolithic VCO chip which provides sine, triangle and ramp waves with excellent linearity and low distortion and high-end matched transistors are used for good CV volt/octave tracking. Internal factory-trimmed adjustments are provided for CV volt/octave and high tracking on each channel.

Control and Signal Routing

By offering waveform and mode adjustments through computer-controlled analog signal routing as well as internal VCA-based mixing circuits, noise-free switching and blending between waveforms is possible. All modes are shown with LEDs on the front panel, and the current frequency of each VCO is displayed on an LCD readout. The use of computer control over the signal routing means that audio signals never pass through the front panel.

Input and Outputs

Inputs are provided on each channel for CV (volt/octave) and FM tuning inputs, PWM and blend CV inputs for driving the wave shaping stages, and a sync input for hard sync effects. Outputs are provided for both the blend circuit output as well as a dedicated pulse output of only the PWM and pulse shaping sections. Two special outputs are provided that contain signals from both channels. The wave mix output offers only the wave signals from each channel, and the XOR output provides a digital multiplication of both channels which works similar to a ring modulator, but outputs square waves.

Cross Modulation Capabilities

In addition to offering two very capable independent VCOs, the cross modulation section allows control of VCO2 from VCO1. Cross mod controls allow pitch, PWM and blend mixing modulation, and the internal PLL and SYNC circuits allow the VCO2 oscillator to be controlled by VCO1 in a variety of different ways without requiring external patch cables. With only an audio output cable attached, an enormous variety of experimental sound possibilities exist. As part of a complete modular system the possibilities are virtually endless.

Features and Specs

  • Eurorack (3U) form factor - 36HP width
  • Dual VCO with independent power supplies per channel
  • Backlit LCD screen with frequency counter for each channel
  • LED indication of selected switch positions and VCO core activity
  • Each channel:
    • 1V/octave CV input - factory trimmed for 1V/octave response
    • Linear FM input with level control
    • Fine and coarse tuning controls
    • Normal VCO frequency range: 2Hz to 15kHz
    • LFO mode switch - period: greater than 70 seconds to 8ms (120Hz)
    • Temperature compensated exponential converter with super-matched transistors
    • Wave shaper with sine, triangle or ramp waveforms - switch selectable
    • Pulse shaper with three pulse types - switch selectable
    • Voltage controlled mixing between wave and pulse waveforms
    • High-end blend VCAs with ultra-low distortion and linear control
    • Sync input for hard syncing of VCO core
    • PWM input with level and offset controls - full deflection with 5Vpk-pk
    • Blend VCA control input with level and offset controls - full deflection with 5Vpk-pk
    • Blend output - output from the blend VCA containing wave and/or pulse waveforms
    • Pulse output - dedicated output from the pulse shaper containing pulse waveform
  • Internal cross modulation controls:
    • Pitch modulation control - exponential frequency modulation of VCO2 from VCO1
    • PWM modulation control - modulate VCO2 pulse width from VCO1
    • Blend modulation control - blend between WAVE and PULSE waves on VCO2 from VCO1
    • Internal PLL mode for locking VCO2 to VCO1
    • Internal Sync mode for syncing VCO2 to VCO1
  • Wave mix output - buffered mix of VCO1 and VCO2 wave outputs - for FM effects
  • XOR output - digital Exclusive OR output from both VCOs - for ring mod-like effects
  • All inputs and outputs are tolerant of +/-12V
  • All outputs drive 10Vp-p with 1K output impedance
  • Requires +12V (200mA), -12V (100mA) - 16 pin Doepfer-style power cable used - approx. 3.5W total power consumption
  • Designed and made in Canada using high quality parts.
  • Warranty: 1 year



No longer available.


Synth Demo #2 - K3020 Dual VCO

Modular Synth: K3020 Dual VCO

Audio Samples

Samples consist of the K3020 Dual VCO, Kilpatrick Audio custom-designed envelope generator, VCA and reverb/delay. The result was sampled by a Yamaha 01v mixer and recorded digitally. No filters or other sound processing was done to the audio.

CV and modulation sources include the K4815 Pattern Generator, K1600 MIDI Converter, a Doepfer LFO as well as the K3020 internal crossmod controls.

Tonal Demo
Several short clips of K3020 playing melodies. Blend and pulse modulation is used. The K4815 generates a sequence on one VCO while a solo is played on the other.

Poly Seq
Polyphonic sequences with both VCO channels. K4815 generates the CV/gate and external MIDI control is used to transpose the pattern.

Square Wave FMod
Using the K4815 to frequency mod VCO2 while VCO1 sweeps the PWM slowly.

Unison Detune
Both VCOs use the same CV input and the oscillators are slightly detuned. The K4815 provides the sequence.

Crossmod Demo
Various pitch, PWM and blend mods, plus SYNC mode experiments.

Low Freak
A low frequency modulation of VCO2 with VCO1. (the very low bass requires big speakers or headphones)

Experimental Sounds
Several short clips of K3020 doing various cross modulation things.