K3021 Master VCO
User Manual
Download a PDF version of the manual here: K3021-master_vco-manual.pdf
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Introduction
When we released the original K3020 Dual VCO back in 2011 people were amazed by the sound and flexibility of the module. The unique blend
circuit, stability and excellent PWM section became a favourite amongst serious modular players. But unfortunately all good things must come to an
end. Some of the components used in the K3020 are no longer available. As well, modern players now request more compact modules. Thus the
K3021 was born! The K3021 Master VCO aims to recreate the flexibility and excellent sound of the K3020 in a small and affordable package. We
hope you will enjoy the K3021 Master VCO!
Setup
The K3021 Master VCO requires only +12V and -12V. Make sure you use a good power supply that is not overloaded. The voltages should measure
as close to +12V and -12V as possible.
The easiest way to get started is to just listen to the output from the BLEND OUT jack and adjust the tuning controls, WAVE switch and BLEND
OFFSET control to check out the various waveforms.
All signals on the K3021 use a range of about -5V to +5V. (10V peak to peak) The exception is the SYNC IN jack which requires a sharp positive
going voltage to trigger.
Jacks and Controls
Tuning and Range
The fine and coarse tuning controls are used to tune the module. The COARSE TUNE control has a range of most of the output range of the module,
and the FINE TUNE operates over about half an octave.
The LFO puts the K3021 into low-frequency oscillator (LFO) mode. By using the blend and pulse functions, very complex LFO waveforms can be
produced. Two LEDs beside the BLEND LEVEL control show whether the internal oscillator core voltage is rising or falling. This can be useful when in
LFO mode.
CV IN, FM IN and FM LEVEL
Tuning CV voltages go into the CV IN and FM IN jacks. The CV IN jack is internally calibrated to respond exponentially with 1 volt per octave and
should work with MIDI to CV converters or other sources of musical pitch voltage. The FM IN jack responds linearly and can be used for special
effects, vibrato, and so on. It is possible to stop the oscillator with a low enough voltage on this jack. The FM LEVEL control attenuates the FM IN