Piezo is a contact microphone preamplifier and CV generator with an integrated envelope follower, gate output, and user-controllable attack and delay parameters. Its front panel features a dedicated tactile zone designed to be scratched, struck, or pressed, making the module itself a playable instrument.
Description
Piezo is an original module inspired by a lineage of contact microphone interfaces: the Mikrophonie by Music Thing Modular (Tom Whitwell), the Ears by Mutable Instruments (Émilie Gillet), and the Radar by Behringer. All share the same foundational concept: turning physical vibrations into usable Eurorack signals.
- Integrated piezo microphone A piezoelectric sensor coupled directly to the panel’s tactile zone captures vibrations from scratching, tapping, pressing, or any physical interaction with the panel surface. The sensor also responds to vibrations transmitted through the case from external sources.
- External jack input A 3.5 mm jack accepts an external contact microphone or any mic-level source. When a cable is inserted, the external input takes over from the internal piezo.
- AUDIO output The amplified signal from the piezo or external input, at modular level and ready for further processing.
- ENV output A CV signal that follows the amplitude envelope of the input. The shape of this envelope is governed by the Attack and Delay knobs.
- GATE output A trigger or gate pulse fired when the input signal crosses the threshold set by the Sens knob.
| Knob | Function |
|---|---|
| Sens | Sets the amplitude threshold above which the GATE output fires. Lower sensitivity requires a louder transient to trigger. |
| Gain | Controls the amplification applied to the piezo or external input before the AUDIO output and the envelope detector. |
| Attack | Sets how quickly the ENV output rises in response to a transient. A fast attack captures sharp hits precisely; a slower attack smooths them into a swell. |
| Delay | Sets the hold or release time of the ENV output and/or the GATE pulse duration after the signal drops below the threshold. |
Technical Specifications
| Parameter | Value |
|---|---|
| Format | Eurorack (3U) and 6HP wide. |
| Power | -12V / +12V |
Circuit Description
Components
Assembly
Front panel
Revisions
Version 0.2
This prototype has a reversed taper on the Sens potentiometer: turning the knob clockwise decreases gate sensitivity rather than increasing it. The module is otherwise fully functional.