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Nekyia Circuits Ouija

VCO/LFO utility

4 HP Eurorack module

An analog VCO/LFO utility combining voltage-controlled glide, white noise, two suboctave dividers, a ring modulator with modulator-level VCA, and a difference rectifier for audio and CV processing.

Features

  • Glide Rate and Glide CV Input affect rising voltages only. Glide Input can smooth saw/square LFOs and fast-attack envelopes, or apply a low-pass filtering effect to audio.
  • The glide circuit cycles by default as a triangle LFO/VCO. Glide Rate sets its frequency, reaching approximately 1kHz at the zero position; Glide CV Input also controls the rate.
  • Glide Rate Indicator provides LED indication of the glide rate.
  • Glide CV Input: +/-5V. VCA CV Input: 10V.
  • White Noise Output can supply an audio layer, oscillator pitch FM, an external sample-and-hold input, or random CV when filtered.
  • Signal Input drives two square-wave frequency dividers. Sub 1 Output is one octave below the input and Sub 2 Output is two octaves below it. With a clock input, they provide divide-by-two and divide-by-four clocks.
  • The ring modulator multiplies Signal Input and Modulator Input. VCA CV Input controls the modulator level and therefore ring-modulation depth.
  • Carrier and modulator are explanatory labels: the multiplication itself has no inherent distinction between the two signals.
  • Difference Rectifier Output provides the full-wave-rectified difference between Signal Input and Modulator Input. It produces positive-only waveforms simultaneously with the bipolar Ring Modulator Output.
  • Audio-rate inputs produce inharmonic metallic sounds; slow control signals can produce complex, nonrepeating waveforms.
  • Remember: disconnect system power before installation and check ribbon-cable polarity. Align the red stripe with -12V on both the module, marked by a white bold line, and the bus board.

Controls & Jacks (13)

  • White Noise Output— Outputs white noise for use as an audio source or as an input to external sampling and filtering utilities.
  • Modulator Input— Accepts the second audio or slow control waveform for ring modulation and difference rectification. Its ring-modulator level is controlled b
  • Glide Output— Outputs the slew-processed input signal or the default cycling triangle waveform, with a maximum frequency around 1kHz.
  • Glide Rate Indicator— Indicates the glide rate.
  • Signal Input— Shared carrier input for the ring modulator and positive input of the difference rectifier; also drives both frequency dividers. Accepts aud
  • Glide Input— Accepts pitch CV, LFOs, envelopes or audio for rising-edge slew limiting; audio receives a low-pass filtering effect.
  • Glide CV Input— Accepts ±5V CV to control rising-edge glide time or the frequency of the default cycling triangle LFO/VCO.
  • VCA CV Input— Controls the VCA governing the modulator signal level and therefore ring-modulation depth; the manual specifies 10V.
  • Glide Rate— Controls slew time for rising input voltages only. In default cycling operation, sets the triangle LFO/VCO rate, reaching approximately 1kHz
  • Sub 1 Output— Outputs a square suboscillator one octave below the Signal Input, or a divide-by-two clock when that input receives a clock.
  • Sub 2 Output— Outputs a square suboscillator two octaves below the Signal Input, or a divide-by-four clock when that input receives a clock.
  • Ring Modulator Output— Outputs the product of the carrier and modulator signals for audio ring modulation or complex bipolar CV processing. For VCA use, patch audi
  • Difference Rectifier Output— Outputs the full-wave-rectified difference between Signal Input and Modulator Input, producing positive-only audio or control waveforms.

How-To Guides

  • Patch voltage-controlled portamento
  • Control the cycling triangle rate
  • Generate square suboscillators
  • Divide a clock
  • Process two waveforms
  • Use the ring modulator as a VCA

Explore the interactive Ouija panel on BleepDex — tap any control to learn what it does.

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