The Befaco VC ADSR DIY Kit is a self-build version of Befaco's 8HP Eurorack envelope generator. Befaco calls it its take on the classic ADSR, made smaller, more capable and easier to use. It suits builders who want an envelope with voltage control over every stage and a gate output for each one. The kit contains all parts needed to complete the module, plus a power cable and four Befaco Knurlies M3 rack screws.
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Voltage control per stage: Attack, Decay, Sustain and Release each have a slider and a dedicated CV input.
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Per-stage gate outputs: each stage has its own gate output that goes high while that stage is active.
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Variable curve: a potentiometer shapes the segments from linear to logarithmic/exponential.
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Gate and trigger operation: in gate mode, release begins when the gate ends. In trigger mode, a single trigger produces an attack-release envelope.
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Manual triggering: a push button fires the envelope, and holding it sustains the envelope.
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Wide time range: attack, decay and release reach up to 10 s. Negative CV pushes attack down to 200 µs and decay down to 400 µs.
The core of the circuit is a dual-transistor current mirror working as a voltage-controlled integrator, combined with switching logic. Because each stage time is under CV control, the envelope can be shaped from other modulation sources as it plays, for example by shortening the attack with velocity or stretching the release from an LFO.
The four stage gates add sequencing and logic options. You can use the end of the attack to fire another envelope, or use the sustain gate to open a VCA or trigger an event elsewhere in the patch. LEDs show any incoming gate or trigger, including the push button, and indicate which stage is currently active.
The front panel is heat-treated aluminium. The module is designed in Barcelona, where Befaco also prepares the kits.