Metabolic Devices - Coherence

Overview

You think LFOs are overly repetitive and chaos CV sources are contextually irrelevant? – Then Coherence is for you! The module uses a unique window comparator, an S&H stage and a divider circuit to derive harmonious melodies and matching rhythms from two arbitrary modulation signals. – Including variations! The results can be very surprising. Thanks to a fully analog circuit design, the performance is excellent.

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Details

Coherence is equipped with two input channels, meant for modulation voltages coming from LFOs, envelopes and the like. One of these signal paths features a bipolar attenuator and an adjustable offset generator. (Control range: -5 V to +5 V.) An application example: If the pitch signals generated by Coherence are too high, simply add a negative offset. The other way round, low melodies can be transposed upwards using a positive offset. If only one modulation signal is available, the offset generator may serve as a fixed voltage source. The inputs of both channels can be swapped quickly via a button.

The window comparator is edited using the potentiometer highlighted in orange. In other words, this control element determines the distance to which the input signals are considered coherent. A CV input with bipolar attenuator allows you to influence the window via modulation signals. A coherence output (marked black) and an incoherence output (marked grey) emit gate signals (+5 V) if the distance between the first and second input signals is smaller respectively larger than the coherence value.

The blue front panel section is responsible for generating melodies. At the heart of the associated circuitry, you’ll find a S&H stage. The calculations performed by the Coherence module to determine pitch CV values are quite complex. The most important factor is which voltages are applied to the window comparator at the moment the S&H stage gets activated. You can choose from several trigger modes via three buttons:

  • First mode: Each time the divider (see below) emits a gate signal, a new pitch CV voltage is generated.
  • Second mode: Each time the input signals at the window comparator are considered equal, a new pitch CV voltage is generated.
  • Third mode: Each time the waveform at the second input channel changes its direction (upward / downward), a new pitch CV voltage is generated.

By pressing several mode buttons simultaneously, two or more trigger types can be combined. A potentiometer allows you to alter the pitch range manually. Besides the note CV output, there is a trigger out (+5 V, 2 milliseconds). This socket becomes active whenever the note voltage changes. Together, the outputs can be used for controlling a synthesizer voice. Notes with sustain phase may be generated by combining the pitch CV output and the coherence output (marked black).

The divider is fed with gate signals coming from the coherence output of the window comparator as well. A divisor (from 1 to 16) can be set via a row of buttons, so that only every x times an incoming voltage is actually passed on by the divider. A trigger input allows you to reset the circuit. Results are emitted via four gate outputs:

  • 1/2 output: Goes high (+5 V) every time a signal is sent from the window comparator to the divider. It becomes inactive again as soon as both input signals are considered equal or incoherence occurs.
  • 2/2 output: Goes high (+5 V) every time both input signals are considered equal. It becomes inactive again as soon as incoherence occurs.
  • Divider output: Goes high (+5 V) every time the number of steps set in the divider is reached. The gate length corresponds to the sum of output 1/2 and 2/2.
  • Remainder output: Goes high (+5 V) every time the step count increases, but the gate signal is suppressed by the divider.
miscellaneous
The most harmonious results are achieved by Coherence when fed with slowly rising and falling signals. – Triangle waves or slow envelope voltages, for instance. In addition to periodic material, one-shots are suitable as well. Waveforms with steep edges, such as a rectangle, often lead to unpredictable results. The same goes for modulation signals fed to the window comparator. Here, however, rectangle or pulse waves may be used to create song structures reminiscent of verse and chorus.
connectors

Two signal inputs
CV input for window comparator
Coherence gate output
Incoherence gate output
Pitch output
Trigger output
Four divider gate outputs

dimensions

3U Eurorack module, 16 HP wide, 25 mm in depth
Power consumption: 50 mA at +12 V and 70 mA at -12 V

Weight
0.2 kg
Article Number
METDcoh
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