VCM20 – £189 + tax & delivery
VCS20 – £189 + tax & delivery

VCM20 – £189

VCM20 MIDI-CV Master Module

One required per set of VCS20

VCS20 – £189

VCS20 Autotune MIDI-CV Module

One VCM20 is required per set of VCS20’s

VCM20 / VCS20 Key Features

This self contained Eurorack expandable Midi to CV converter/calibration system offers an uncomplicated solution to the problems of tuning and scaling both vintage synthesisers and modern VCO Eurorack modules. With 16 bit voltage resolution and a tune time of 10 seconds. The unit can compensate for VCO alignment issues and environmental factors that cause tuning drift with the push of a button. Its Digital Automatic Audio Gain Control Circuitry (DAGCC) enables the unit to be connected to most synthesiser outputs, and has been tested on a large array of makes and models. While obviously not being capable of fixing the problems of faulty circuitry it will however save time and money on re–calibration, and ensure the technical side of synth ownership doesn’t impinge on the creative process.

The VCM20 master module has an LED (Light Emitting Diode), an increment push button to select the MIDI (Musical Instrument Digital Interface) channel, and MIDI IN and MIDI THRU sockets.

The VCS20 slave module has four 3.5mm jack sockets for communicating with the outside analogue synthesiser world, which is where the tuning action really gets going: CV1 connects to the synthesiser’s pitch control voltage and can be set to either V/oct (Volts per octave) or Hz/V (Hertz per Volt); CV2 is mapped to keyboard velocity — typically to control a VCF (Voltage Controlled Filter) or VCA (Voltage Controlled Amplifier); the 11 Volt GATE output can be set to either V-Trig (Voltage Triggers) or S-Trig (Switch Triggers), its use being indicated by the Gate LED; the VCO input connects to the synthesiser’s waveform or audio input and allows the VCS20 slave module to read audio frequencies during the calibration process — a square, sine, or sawtooth waveform without modulation is recommended for doing this.

The oscillator output can either be split or an unused waveform connected in the case of modular system setups while with typical hardwired analogue synthesisers it’s a case of splitting the audio output or, in most cases, using the headphone output. Either way, the synthesiser needs to be set to output a single oscillator without filter or modulation with the VCA envelope set to zero attack, zero decay, full sustain, and zero release. For the most accurate calibration of the control voltage the synthesiser’s oscillator range should be set to 8’ or its initial oscillator frequency set midway.

Having correctly connected everything, pressing the VCS20 slave module’s Tune button automatically tunes the analogue synthesiser, compensating for calibration errors between 0.5 and 1.5 V/oct. (During the tuning process, the Gate opens and its associated LED lights up, going out once complete.) Calibration data is duly stored — solving the problem with a neat solution! Still better, the VCS20 slave module retains the calibration data on power down — no need, necessarily, to repeat the process.

Suffice to say, Vince Clarke’s canny vision of an all-in-one MIDI-to-CV convertor with auto-calibration has truly become reality with the Clarke Auto Tune system since it is possible to set the individual MIDI channel for each VCS20 slave module and see which MIDI channel a slave module is set to at any time by simply pressing its Show button.

Beauty is in simple things, after all. Equally easy, the VCS20 slave module’s Oct. (octave) button transposes the incoming MIDI signal by one octave with each push, cycling around four octaves — useful if the synthesiser’s range circuit is detuned.

Don’t forget, each VCS20 slave module connected can be individually set to work with V/oct or Hz/V synthesisers so a variety of older and newer analogue instruments can be calibrated and automatically tuned by the Clarke Auto Tune system.

Start with a VCM20 master module and one VCS20 slave module, maybe? Then simply add more VCS20 slave modules as your analogue instrument collection grows… guaranteed to stay in tune, each and every one of them — just like Vince Clarke’s Brooklyn-based sizeable collection of vintage and modern synthesisers! Synth-pop songwriting success, sadly, cannot be guaranteed.



For video manual and specifications please visit