nekyia-circuits-occult

Nekyia Circuits Occult

Thru-Zero Waveshaping VCO

12 HP Eurorack module

Occult is an analogue triangle-core VCO/LFO with through-zero and exponential FM, hard and soft sync, and nine simultaneous waveform outputs. Its Pulser waveshaper and Shaper crossfader provide additional timbral control.

Features

  • Nine simultaneous outputs: Sine, Triangle, Square, Pulse, PWM Saw, Sub 1, Sub 2, Shaper and Pulser.
  • Coarse spans approximately ten octaves, extended by Octave. Fine spans approximately six semitones. V/Oct Input tracks precisely over at least seven octaves.
  • Oscillator Rate is a bipolar LED showing oscillator speed, particularly useful in LFO mode.
  • TZFM Amount attenuates TZFM Input. Through-zero FM reverses oscillator direction at negative frequencies. The input is AC-coupled so DC offsets do not destabilize pitch. Remember, high TZFM Amount settings can remove a clearly defined pitch.
  • Exponential FM Input uses 1 V/oct scaling. Exponential FM changes perceived carrier pitch, and the resulting pitch does not track chromatically. Slow modulation can produce vibrato.
  • PWM sets the base width for Pulse Output and PWM Saw Output. At the midpoint, Pulse Output has a 50% duty cycle. Remember, pulse widths of 0% or 100% produce no sound.
  • PWM Saw Output produces a pure saw with PWM at zero. At the midpoint it produces a double saw, one octave above the oscillator frequency.
  • Pulser adds odd harmonics to its sine or triangle input using two pulse signals. Symmetry changes comparator thresholds and pulse widths; Symmetry CV Input modulates this behavior.
  • Harmonics controls the mix of symmetrically placed positive and negative pulses with the original Pulser input signal. Harmonics CV Input modulates that mix.
  • Shape and Shape CV Input control a crossfade between the normalled sine signal and the internal Pulser signal.
  • With Shaper Signal Input unpatched and Shape at zero, Shaper Output supplies a slightly saturated sine, distinct from the pure Sine Output. Patching Shaper Signal Input replaces this normalled sine with another Occult waveform or an external signal.
  • PWM CV Input, Symmetry CV Input, Shape CV Input and Harmonics CV Input each have a +/-5 V range.

Controls & Jacks (31)

  • TZFM Amount— Attenuates the signal arriving at TZFM Input to set through-zero FM depth; high settings can produce sounds without a clearly defined pitch.
  • Fine— Fine frequency adjustment over approximately six semitones.
  • Coarse— Sets oscillator pitch over approximately ten octaves; the Octave switch extends the available range.
  • Shape— Crossfades between the Shaper signal input, normalled to a slightly saturated sine wave, and the internal Pulser signal.
  • Harmonics— Controls the mix of symmetrically placed positive and negative pulses with the original sine or triangle signal, changing Pulser harmonic co
  • PWM— Sets base pulse width for the Pulse and PWM Saw outputs. The middle position produces a 50% pulse and a double saw; zero produces a pure saw
  • Symmetry— Changes Pulser comparator thresholds and the widths of the two generated pulses, altering waveform symmetry.
  • PWM CV Input— ±5 V modulation input controlling the pulse width of the Pulse and PWM Saw outputs.
  • V/Oct Input— 1 V/oct pitch input with precise tracking over at least seven octaves.
  • Harmonics CV Input— ±5 V modulation input controlling the Pulser harmonics amount.
  • Symmetry CV Input— ±5 V modulation input controlling Pulser symmetry and the widths of its generated pulses.
  • Frequency Range— Selects LFO operation in the up position or audio-rate VCO operation in the down position; VCO operation spans approximately 20 Hz to above
  • Octave— Transposes the oscillator up one octave in the up position or down one octave in the down position.
  • Sync Input— External oscillator synchronization input, operating in hard or soft sync according to Sync Mode; sharp rising-edge waveforms work best.
  • Sine Output— Pure sine waveform output at audio or LFO rates, separate from the slightly saturated sine available through Shaper.
  • PWM Saw Output— Variable-width saw waveform output; PWM at zero gives a pure saw, while its middle position gives a double saw at twice the oscillator rate.
  • Sub 1 Output— Suboscillator output one octave below the square wave; provides half the base oscillator rate in LFO mode.
  • Shape CV Input— ±5 V modulation input controlling the Shaper crossfade between its signal input and the internal Pulser signal.
  • TZFM Input— AC-coupled through-zero linear FM input; modulation depth is set by TZFM Amount.
  • Sync Mode— Selects soft sync up or hard sync down. Soft sync resets only near the end of the oscillator cycle; hard sync resets on the external sync si
  • Square Output— Dedicated square waveform output at the oscillator frequency, usable at audio or LFO rates.
  • Shaper Signal Input— Audio input for one side of the Shaper crossfader; patching replaces its normalled internal sine wave with the supplied signal.
  • Shaper Output— Shaper crossfader output blending the normalled sine or external signal with the normal or inverted Pulser signal; also supplies complex mod
  • Pulser Output— Pulser waveshaper output with timbre determined by Symmetry, Harmonics and Pulser Wave; works at audio or LFO rates and can exceed 10 Vpp.
  • Triangle Output— Triangle waveform output at audio or LFO rates.
  • Pulse Output— Variable-width pulse output at audio or LFO rates; PWM at the middle position gives a 50% duty cycle, and width can reach 0% or 100%.
  • Sub 2 Output— Suboscillator output two octaves below the square wave; provides one quarter of the base oscillator rate in LFO mode.
  • Exponential FM Input— Exponential FM input with 1 V/oct scaling; accepts audio-rate modulation and slow voltages for effects such as vibrato.
  • Oscillator Rate— Separate bipolar LED indicating oscillator rate, particularly useful during LFO operation.
  • Pulser Wave— Selects the internal waveform feeding Pulser: sine in the up position or triangle in the down position.
  • Shaper Pulser Polarity— Selects normal Pulser polarity up or inverted Pulser polarity down for the signal feeding the Shaper crossfader.

How-To Guides

  • Patch classic through-zero FM
  • Create envelope-controlled TZFM
  • Shape TZFM into percussion
  • Crossfade another waveform with Pulser
  • Explore soft-sync Pulser textures
  • Patch LFO rhythmic ratios

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

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