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Hertz Donut MK3

Industrial Music Electronics Hertz Donut MK3


Complex digital oscillator with unison detune, programmable 3x4 modulation matrix mixer and external input. Intricate arrangements of phase distortion, thru-zero frequency modulation, and complex oscillation are instantly morphable and recallable through a voltage-controlled preset manager. Suitable for genre-targeted sequenced basslines, synthesis of stone, glass, and steel tones, and simulation of the acoustic properties of industrial machinery.

The Hertz Donut Mark III’s main oscillator shapes its timbre by distorting the phase of a waveform lookup ramp, offering a linear growth of brass overtones from a simple sine wave whilst performing with exceptional clarity under heavy frequency modulation. The simulated resonance peak familiar to enthusiasts of phase distortion is also present and continuously controllable. The beloved “fractal” distortion from previous iterations of Hertz Donut is simultaneously available. The three waveform parameters operate in a modeless timbre space fully morphable under preset and shared manual/CV control, exhibiting stunning spectral evolutions that are intensified through the module’s internal modulation bus. The fold knob is assignable to control one of the three parameters at a time, with the CV input also assignable to any of the three.

Two sinusoidal modulation operators are mixed to four modulation destinations with an external audio input. The operators may be locked to several precise frequency ratios of the main oscillator, or set to be otherwise subordinate. The three sources may modulate each other’s frequencies, or the amount of phase or fractal distortion. A plethora of control voltage inputs allow full control of the patch, reacting within a +/- 10V range. The first operator has a calibrated 1v/oct control voltage input and fine tune control, for use as an independent oscillator augmented by the modulation bus. The modulation mix is placed under the influence of a master control, so that a single knob and CV input control the degree of modulation in the entire module. Each sound that you design will have a unique and intense behavior of this modulation control.

The preset manager stores 8 entire panel/menu states for instant recall under manual or voltage control. The control can also cause the creation of elegantly randomized preset data. The preset manager can be placed into a morphing mode where it assumes control of the various parameters, smoothly fading between entire panel states and generating very complicated sounds that are not easily described.

The unison detune function mixes in a nearly identical copy of the sound with slightly offset frequency, or optionally in octave or fifth intervals. The Hertz Donut operates at 96khz for a minimum of sampling byproducts, able to consistently and competently generate ornate digital beauty and jagged swaths of sonic mayhem. The auxiliary output presents the output of one or both modulation operators, also with optional unison applied. The nearby mix output is an analog sum of the Main and Aux outputs, facilitating parallel FM algorithm construction. Perfect, genuine, complete, crystalline, pure.

• Main oscillator with resonant, phase, and fractal distortions (CV and manual knob destinations selectable)
• 8 octave tuned CV response (1V/octave)
• 2x sinusoidal modulation operators with frequency interval lock or free operation
• External thru-zero FM input
• 4x3 modulation matrix mixer with master amount control
• 128x32 OLED display providing realtime note, frequency, and modulation information, as well as menu access to deep settings
• All parameters may be placed under control of morphing preset manager with 8 onboard presets (nonvolatile)
• 96 kHz sampling rate


All Mark III Series modules from Industrial Music Electronics come with a standard preset manager interface. This manager is the product of determined user interface research, and the successful solution to a number of modular synthesizer performance questions. The MORPHING PRESET MANAGERenables immediate control and recall of all panel parameters and significantly reduces the number of patch cords required to recreate carefully patched sounds in a live situation. It provides a new dimension of intense sonic transformation suitable for deep sound design or extended performance technique, for when you just don’t have enough cables or limbs to move the controls in the way that your imagination demands.

The interface consists of an OLED display, rotary encoder, CV input, and an attenuator control. The CV input responds to positive and negative voltages. Each module has a setting to limit the operation of the preset manager: for example, the Hertz Donut and Piston Honda oscillators’ managers can operate ONLY on the wave parameters, or on ALL controls including the frequency. The user may prefer to use the manager only as a timbral control, or also as the master pitch control in a sequenced performance. The interface and voltage thresholds are standardized across all Mark III modules, so a simple unbuffered multiple is sufficient to simultaneously drive the preset state of several modules.

When activated, the manager engages one of eight active presets. The preset may be selected by turning the encoder or by manipulating the CV input. The controls may be manipulated while this mode is active, and the module’s CV inputs will also respond. To change the data that is stored in the preset memory, hold down the encoder button while moving the control you’d like to change. The eight presets can then be stored to nonvolatile memory that will endure power-downs and firmware upgrades.

When Morph mode is active, the managed controls are put under full control of the preset. The CV inputs will still respond to external voltages. Select a “base” preset by turning the rotary encoder: its button and menu settings will become the basic setting for the morph. The Morph CV input (and the attenuator/offset knob) will then morph ALL of the managed knob/slider controls from one preset to the next, operating over the entire active memory. For example, while using a Piston Honda Mark III, imagine the three waveform morphing axes setting a point within a “cube” of waveforms. By enabling the morphing presets, you are traveling in a straight line between each of these points, navigating a 3-dimensional timbral pathway using a single control voltage. This is something that would take several channels of programmed control voltages (and much more time) to repeatably recreate without the preset manager.

Stored presets may be recalled from nonvolatile backup at any time. The behavior of the CV input and attenuator can be set in several different ways, from the expected attenuator behavior, to offset, to triggered preset advance, to triggered random preset generation. The preset menu provides initialization and randomization functions that work on the sound even if the preset manager is not active. The random generator tactfully selects sound parameters with carefully considered probabilities and awareness of other states of the preset, resulting in a new tone that more often than not sits in a previously unexplored “sweet spot” of the module’s possibilities.

3U Eurorack module, 17HP wide, 25mm deep.