Janus LFO

Poly LFO with a gated delay · Vulpus Labs

A versatile polyphonic LFO with a gate input. LFO start phase and delay can be synchronised to note onset, and polyphonic CV inputs enable LFO rate and delay duration to be modulated per channel.

IN

GATE — poly gate input. A gate is high above 0 V; a crossing from at-or-below zero to above it is a trigger.

With the jack empty the module free-runs at full depth, phase-locked across every lane. The delay is forced to zero and PHASE is forced free-running, because there is no note to fade in from or sync to.

The five switches

PHASE — FREE (down) / GATE (up). What a gate does to the sweep.

• FREE — phase ignores gates. Notes arrive wherever the sweep happens to be.
• GATE — the sweep restarts at zero deviation when a phrase or note begins.

MODE — OR (down) / IND (up). Whether gating is per phrase or per voice.

• OR — One ramp and one phase for everything, armed by the first gate to trigger and disarmed by the last gate to release. Play into silence and it restarts; add a note to a held chord and nothing restarts. The cost is that a note played later in a legato phrase arrives at full depth with no fade of its own.
• IND — each voice's own gate arms its own ramp, and with PHASE at GATE, its own sweep. Later notes fade in from their own onset. Sixteen lanes at one rate with unrelated phases shimmer rather than move as one body.

RETRIG — LOOP (down) / ONCE (up).

• LOOP — the sweep runs continuously.
• ONCE — one cycle per trigger, then hold. The run ends exactly one cycle from where it began. Useful for making the LFO a one-shot envelope shaped by whichever waveform is selected. With PHASE at FREE it stops wherever it started and holds that value as a standing offset until the next trigger.

SYNC — Hz (down) / TEMPO (up). What the rate fader reads in. This is tempo sync, not phase sync.

POLARITY — + / BI (centre, default) / −. Which side of zero the output sits on.

MOTION

RATE

Fader — 0.05 Hz to 30 Hz, exponential, resting at the centre of that travel. Two scales, depending on how the SYNC switch is set: Hz on the left, DIV on the right. In TEMPO the travel selects one of twenty divisions in equal bands, 4/1 at the bottom to 1/32T at the top — 0.125 Hz to 24 Hz at 120 BPM.

AMOUNT (−/+, centre detent) over MONO and POLY — the two CV jacks are summed and the attenuverter scales the sum. Full amount and ±5 V ranges between half the fader's rate and double it.

One cable in MONO offsets the whole module; a fan from Janus KEY (forthcoming) in POLY spreads the lanes. Both at once does both.

DELAY

Fader — 0 to 5 seconds. A linear fade-in from zero to full depth.

With the GATE jack empty the fader does nothing.

AMOUNT over MONO and POLY, as RATE. Summed then attenuverted; ±5 V at full amount covers the whole travel. A fan into POLY gives every voice its own fade time.

SHAPE

WAVE — six options, read downward: sine, triangle, saw up, saw down, pulse, random. Smooth shapes at the top, stepped ones at the bottom. Triangle is the default and sits second from the top.

None of these shaped is band-limited. Saw, pulse and random step, deliberately: a modulation source's job is to deliver the step, and whatever consumes it is free to smooth it. Use Janus SLU (forthcoming) if you want it rounded.

Random is sample-and-hold: a new value at every phase reset, which means both the wrap at the end of a cycle and a gate sync. So RATE sets how often the value changes, and a synced note gets a fresh one at its onset. Lanes resetting on the same sample draw the same value, so OR holds every lane together and IND comes apart exactly when the sweeps do.

PULSE WIDTH (centre detent, a square) with its own AMOUNT and mono CV. High first, so a gate-synced pulse lifts the note it starts on rather than dropping it. Only the pulse waveform reads it. The tooltip reads the duty as a percentage high.

OUT

OUT — poly, ±5 V at full depth in BI. One value per lane always, whatever the mode.