hertz-donut-mk3

Industrial Music Electronics Hertz Donut mk3

Thru-zero FM meets phase distortion in one complex oscillator

18 HP Eurorack module

The Hertz Donut Mark III is a complex oscillator combining phase distortion and thru-zero frequency modulation, drawing on mid-1980s digital synthesis techniques. It features a 3x4 modulation matrix, three phase distortion parameters (Phase Distortion, Umbrage, Resonance), two internal FM operators, an external audio input, unison detune, and a morphing preset manager. Musically it excels at evolving metallic timbres, bell-like FM textures, buzzy brass-style tones, and glassy chorus pads.

Features

  • Thru-zero frequency modulation (TZFM) carrier oscillator
  • Three phase distortion waveform parameters: Phase Distortion (PDist), Umbrage (fractal/fuzz), Resonance (virtual resonance)
  • 3x4 modulation matrix routing Operator A, Operator B, and External Input to four destinations each
  • Two internal FM operators (sine wave generators) with Quantize, Follow, and Free frequency modes
  • External audio input (modular level, 10Vpp) as third modulation source
  • Master modulation amount control with CV input
  • Operator A: 1V/Oct CV input and fine tune knob
  • Operator B: tuning knob only (no 1V/Oct or fine tune)
  • A-B Link option causes Operator B to follow Operator A frequency
  • Unison detune mode: slight detune to octaves and fifths
  • Selectable AUX output: Op A, Op B, Op A+B sum, or digital XOR
  • MIX output: analog sum of MAIN and AUX outputs

Controls & Jacks (38)

  • Fold Select— Selects which waveform parameter is modified by the Fold knob: Phase Distortion (PDist), Umbrage, or Resonance. Hold encoder button and pres
  • Coarse Tune— Sets the coarse tuning frequency of the primary oscillator. Large orange knob in normal mode.
  • Audio Input— Full-bandwidth audio input for external modulation sources and complex modulation patches.
  • Fine Tune— Sets the fine tuning frequency of the primary oscillator. Small knob in normal mode. Set to middle position for C0 (16.35 Hz) when Coarse Tu
  • Fold— Controls phase distortion and waveform modification. Modified parameter is selected by Fold Select button (PDist, Umbrage, or Resonance).
  • Modulation Operator 1 Level— Controls the modulation amount from Operator 1.
  • Operator 1 Frequency— Sets the frequency of Modulation Operator 1.
  • Encoder— Rotary encoder button for menu navigation, selection, and parameter editing. Hold and press another button to access menus.
  • Main Output— Primary audio output containing the straightforward result of the primary oscillator with phase distortion and FM modulation.
  • Operator 2 Frequency— Sets the frequency of Modulation Operator 2.
  • Operator 2 CV Input— Control voltage input for Operator 2 frequency modulation.
  • Fold CV Input— Control voltage input for modulating the Fold parameter. Destination selectable in oscillator menu.
  • Modulation Operator 2 Level— Controls the modulation amount from Operator 2.
  • Operator 1 CV Attenuverter— Attenuates the CV input for Operator 1 with nonlinear curve.
  • Modulation Operator 3 Level— Controls the modulation amount from Operator 3.
  • Operator 3 Frequency— Sets the frequency of Modulation Operator 3.
  • Operator 2 CV Attenuverter— Attenuates the CV input for Operator 2 with nonlinear curve.
  • Master Modulation Level
  • CV Input— Bipolar control voltage input for vibrato and other modulations. Attenuated by nearby knob. Accepts ±10V, musically useful range ±5V.
  • Total Modulation Amount— Simplified control for the total effect of the modulation bus on the primary oscillator.
  • Operator 3 CV Attenuverter— Attenuates the CV input for Operator 3 with nonlinear curve.
  • Modulation Operator 4 Level
  • Fold CV Attenuverter— Attenuates the Fold CV input with nonlinear curve for subtle to full-swing modulation.
  • Aux Output— Auxiliary output from the auxiliary oscillator. Behavior is selectable in menu.
  • Operator 3 CV Input— Control voltage input for Operator 3 frequency modulation.
  • Mix Output— Analog combination of Main and Aux outputs.
  • Modulation Bus CV Input— Control voltage input for the total modulation bus amount.
  • SYNC
  • 1V/Oct Input— Accepts 1 volt per octave control voltage from sequencer, quantizer, or keyboard. Set C0 to 0 volts for display/frequency matching.
  • 1V/OCT
  • Operator 1 CV Input— Control voltage input for Operator 1 frequency modulation.
  • Preset Button 1— Loads or saves preset 1. Part of the Mark III morphing preset manager.
  • OLED Display— OLED display showing current settings, menu options, virtual sliders for fold parameters, and note information. Auto-turns off after 10 minu
  • Preset Button 3— Loads or saves preset 3. Part of the Mark III morphing preset manager.
  • MOD
  • EXT— External/menu button. Hold encoder button and press to access global options menu.
  • CV Attenuverter— Attenuates the CV input (bipolar vibrato/modulation) with nonlinear curve.
  • Preset Button 2— Loads or saves preset 2. Part of the Mark III morphing preset manager.

How-To Guides

  • Save a Preset
  • Load a Preset
  • Edit and Update a Preset
  • Reload Presets from Memory
  • Initialize All Presets
  • Randomize Current Preset
  • Factory Reset
  • Evolving FM Brass Tone
  • Glassy Unison Chorus Pad
  • TZFM Metallic Bell
  • CV-Controlled Preset Morphing Performance
  • Dual Oscillator Detuned FM Pair

Explore the interactive Hertz Donut mk3 panel on BleepDex — tap any control to learn what it does.

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