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.
