Janus ENV

Sixteen-lane ADSR with a retrigger input · Vulpus Labs

A polyphonic envelope generator with one advanced feature and one unusual one.

The advanced feature is support for two retrigger modes, one which resets the envelope to zero and restarts the attack phase, and another which restarts the attack phase from wherever the envelope just was.

The unusual one is simulating the behaviour of software-generated envelopes in digitally controlled 80s polysynths by providing a "grain" control that sets how often the envelope level is updated, with results ranging from a wholly smooth envelope curve to a subtly stair-stepped one. The stair-stepping introduces sidebands into a signal when the generated envelope is used to modulate its amplitude: it's a period "character" feature.

The ADSR timing is duration-based rather than rate-based: if a phase takes 200ms, it takes exactly that long to get from wherever it starts to wherever it ends regardless of how far apart they are.

GATE, TRIG and the two outputs

GATE — poly. The sustain phase continues while the input is high, and the envelope drops into its release phase when the input turns low.

TRIG — poly, edge-sensed. The retrigger sensor.

OUT + — poly, 0 V to +5 V. Unipolar, which is what Janus VCF's ENV input and Janus SUM's ENV IN both expect.

OUT − — the same contour multiplied by minus one: 0 down to −5 V.

ENV

Sliders controlling the duration of each envelope phase:

SHAPE

Control over the envelope's contours.

RISE and FALL

0 is a straight line, 1 is a sharp exponential curve, intermediate values lie in between.

RISE is the attack. FALL is the decay and the release together.

LOCK

The small button at the right-hand end of the SHAPE rule ties the two curve faders: press it and FALL comes to RISE, and from then on moving either moves both.

GRAIN

The scan the envelope is written at, and the stairs that come of it.

The module can pretend to be emitting an 80s software-generated curve where each per-voice control voltage is a sample-and-hold refreshed once per pass of the CPU's scan, so a fast envelope climbs in steps rather than in a ramp. This fader controls the refresh interval of that scan.

It is inaudible on a slow envelope, by construction.

The sixteen lanes are staggered across the interval rather than refreshed together, which softens the effect.

RETRIG

ZERO (down, the default) / CONT (up). What a trigger does to a lane that is still up when it arrives. The instrument settles neither, because it has no retrigger input at all.

ZERO falls to zero first, then attacks from there. The fall is short, straight and at a fixed rate — two milliseconds from full scale, proportionally less from lower down — so it reads as the front of a note rather than as a click, and it is longest where the click would have been loudest. It is not part of the attack and does not come out of its time: a retrigger from the top costs two milliseconds and then takes the whole attack time.

CONT climbs from wherever the lane is. Nothing falls and nothing jumps, and a retrigger under a held chord is inaudible as an event.