Utilities

Gates

Gate and trigger toolkit - edge detection, flip-flop, gate length shaping, and gate delay.

What is a Gates?

A gate utility is a small toolkit for the gate domain - the binary world of triggers and gates that runs in parallel with the CV and audio domains in a modular synth. While oscillators and filters work with continuous voltages, gates are simple HIGH/LOW pulses that mark events: a clock tick, the press of a key, the start of a note. Gate utilities reshape, divide, delay, and detect those pulses.

The most basic operation is edge detection. Most modules respond to a gate's level - HIGH means open, LOW means closed - but some operations need to fire only at the transitions. A rising edge (LOW becoming HIGH) marks the start of a note. A falling edge (HIGH becoming LOW) marks the end. An edge detector outputs a brief pulse on each transition, regardless of how long the gate stays high after - so it converts a sustained gate into a pair of instantaneous triggers. Patch a long held gate into a rise detector and you get one short trigger; nothing more, no matter how long you hold.

Next up is the flip-flop - a single bit of memory that toggles on every rising edge. Feed it a clock and the output is the same clock at half the rate: a ÷2 divider. Two complementary outputs (FLIP and FLOP) give you two clocks 180° out of phase. Daisy-chain flip-flops and you get ÷4, ÷8, ÷16. The whole clock divider family is just chained flip-flops underneath.

Gate length shaping reshapes a gate to a fixed duration regardless of how long the input gate held. A short trigger comes in; a 200ms gate goes out. Useful for driving things that expect gate-length controls articulation - a VCA envelope with sustain, a delay with gate-controlled feedback, a reverb with gated tail.

Finally, gate delay postpones a gate by a fixed time. Feed two voices from the same trigger but delay one by a few milliseconds and you get automatic flam - the percussionist's term for a near-simultaneous double hit, slightly offset. Longer delays (hundreds of ms or seconds) build up call-and-response patterns from a single trigger source.

Our Gates

Our Gates module gathers all the standard gate operations into one panel: RISE and FALL edge detectors, a FLIP/FLOP toggle pair, a GATE length shaper, a DLY delay, and an EOC end-of-cycle pulse - plus an external TRIG input that mixes into the same edge detection logic and a RESET input that clears the flip-flop. Seven outputs from three inputs.

The LENGTH knob sets the duration for both the GATE shaper and the DLY delay simultaneously, ranging from 1ms to 10 seconds on an exponential curve. A Len CV input adds modulation - patch an LFO into it and the gate length wobbles in time, creating natural-sounding articulation variation. The two operations share the LENGTH parameter intentionally: when the GATE shapes to 250ms, the DLY also delays by 250ms, so a flam-style patch (gate to one voice, DLY to another) automatically times the offset to the gate length.

The EOC output fires a brief pulse at the falling edge of the shaped GATE, so you can chain envelopes or sequencers to fire when the previous gate finishes. The RESET input forces the flip-flop back to its initial state - tie it to a beat-1 trigger and your ÷2 divider always lands on the downbeat, regardless of when you started the patch.

In a patch

Edge detectors are the bridge between gate-driven and trigger-driven modules. Some envelopes want a gate (held HIGH for the note's duration); some drum voices want only a trigger (a single short pulse). Patch a gate through a RISE detector to feed a trigger-only voice from a sustained source.

The flip-flop builds rhythmic structure out of a single clock. Patch a 16th-note clock into FLIP and you get an 8th-note pattern. Patch FLOP from the same module to a different voice and you get an 8th-note offbeat. Two outputs, two interlocking rhythms, from one clock and one module.

The GATE shaper decouples a sequencer's gate length from your articulation choice. A step sequencer may output its gates at a fixed length tied to step length; if you want short staccato or long legato regardless of tempo, run the gate through the shaper. Modulate LENGTH CV with an LFO and the articulation breathes over time.

Inputs

GATE (gate) — Main gate input. Rising and falling edges are detected for the RISE, FALL, FLIP/FLOP, GATE, and DLY outputs.
TRIG (gate) — Separate trigger input. Can be used independently of the main gate for edge detection.
RST (gate) — Reset input. A rising edge resets the FLIP/FLOP toggle to its initial state.
Len (cv) — Length CV modulation. Adds to the LENGTH knob, allowing dynamic control of gate duration and delay time.

Outputs

RISE (gate) — Rising edge detector. Outputs a short trigger pulse on each rising edge of the gate input.
FALL (gate) — Falling edge detector. Outputs a short trigger pulse on each falling edge of the gate input.
FLIP (gate) — Toggle output A. Goes HIGH on odd triggers, LOW on even triggers. Alternates with FLOP.
FLOP (gate) — Toggle output B. Goes HIGH on even triggers, LOW on odd triggers. The complement of FLIP.
GATE (gate) — Reshaped gate output. Fires a gate of LENGTH duration on each rising edge, regardless of the input gate width.
DLY (gate) — Delayed gate. A copy of the input gate delayed by LENGTH. Useful for creating echo-like rhythmic offsets.
EOC (gate) — End-of-cycle trigger. Fires a short pulse when the reshaped GATE output falls. Useful for chaining events.

Controls

Length — Gate duration and delay time from 1ms to 10 seconds. Controls both the reshaped GATE width and the DLY time.

Inspired by

A grab-bag of gate-domain operations that you find scattered across half a dozen modules in a hardware rack: edge detectors, a divide-by-two flip-flop, a gate length shaper, and a delay line for triggers.

Doepfer A-162 Trigger Delay
Joranalogue Transit 4
classic gate utilities

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