listen: a 12 HP repetition detector by daylight noise

listen

12 HP · repetition detector

It notices when your patch has stopped changing. On every clock it samples a gate or a CV, and it counts the loops that come round the same, a light under its name growing brighter all the while. After PATIENCE of them, HEY fires, and again every loop until something changes. The moment it does, LISTEN fires and the count drops to nothing.

How it counts

Every rising edge at CLOCK is a step, and IN is sampled at each one. Each step is compared with the step one loop earlier. Two samples are the same when they're on the same semitone, so a gate's 0 and 5 V work, and so do a sequencer's notes.

A loop is LOOP steps. At the end of each one, if no more of its steps differed than SAME allows, that loop came round unchanged and the count goes up by one.
PATIENCE is how many of those it takes. Then HEY fires at the end of the loop, and again at the end of every unchanged loop after.
A change: the moment a loop has differed by more than SAME allows, LISTEN fires (if the count had reached one), and the count and BORED drop to nothing.
The light follows BORED, faintly lit when nothing has counted yet. It flashes twice on every HEY, and fades slowly from bright on LISTEN.
No clock, no steps. It never runs on its own, and until a whole loop of history exists, nothing counts.

The panel

Three knobs, two inputs and three outputs, every part on the line's lattice and mirrored about the middle. The outputs are knocked out of white.

LOOP

How many steps make a loop: 1, 2, 3, 4, 6, 8, 12, 16, 24, 32, 48 or 64. All the way down is AUTO: it finds the loop itself, the shortest that the recent steps repeat at, up to 64 steps. Until it has one, the input counts as changing.

AUTO · 1 to 64 steps

SAME

How many steps of a loop may differ and the loop still count as the same: none, all the way down, up to a quarter of the loop. For a loop that drifts a little and should still bore it.

none to a quarter

PATIENCE

How many unchanged loops before HEY: 1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 24 or 32. BORED climbs a step for each of them, to 10 V.

1 to 32 loops

The light

Under the name, between the moth's antennae: one frosted cool-white light. Brighter the longer the patch sits still, two quick flashes on HEY, a slow fade on LISTEN.

follows BORED

CLOCK: every rising edge is a step.

IN: the gate or CV it watches, −10 to +10 V, sampled half a millisecond after each clock so a sequencer's new step has landed.

BORED: the count over PATIENCE, as 0 to 10 V, held at 10 V once the count reaches PATIENCE.

HEY: a 10 ms trigger at the end of the loop where the count reaches PATIENCE, and of every unchanged loop after.

LISTEN: a 10 ms trigger the moment a settled loop changes.

Patching it

HEY into anything that changes things: a sequencer's mutate or random input, a drum machine's fill, a random source's trigger, a reset. The loop then changes only once it has been heard PATIENCE times, and the rack never sits on one loop too long.
LISTEN to mark the change: a crash, an envelope, a reset somewhere else, the moment the new loop lands.
BORED into a filter, a VCA or a wavefolder, so something builds while nothing changes and falls away when something does.
Nothing in IN reads 0 V every step, a loop that never changes, so HEY becomes a divider: quiet for PATIENCE loops of LOOP clocks, then a trigger every LOOP clocks.

The art is a death's-head hawkmoth drawn to the light, in a halftone of exposed gold: the skull on its back under SAME, its wings running off both sides past LOOP and PATIENCE, its antennae reaching up either side of the light.

Inside

One board right behind the panel, every knob and jack straight behind its hole. An RP2350 runs the engine; it reads IN and the three knobs against a 3.000 V reference, sets BORED through an MCP4822 and an op-amp, and drives HEY and LISTEN to 5 V. The light is a 5 mm frosted LED standing off the board, its dome flush in the panel's 6 mm hole, dimmed by PWM.

All of it is generated from code. One table places every knob and jack and drives the panel, the board and this page, and the model below is drawn from the same files.

The panel with its knobs on and the light lit.

Drag to look around. Lift the panel and the light stays on the board.

Specs

Format

Standard: Eurorack, 3U
Width: 12 HP (60.66 × 128.5 mm)
Panel: FR4, black mask, gold (ENIG) art
Controls: LOOP, PATIENCE, SAME
Light: One 5 mm frosted cool-white LED
Power: +12 V about 65 mA, −12 V about 6 mA (the design's estimates); 10-pin header

I/O

CLOCK: Rising edges, high above about 1.4 V, 100 k
IN: Gate or CV, −10 to +10 V, 100 k
BORED: 0 to 10 V, 1 k out
HEY, LISTEN: 5 V triggers, 10 ms, 1 k out
Unpatched: IN reads 0 V

Engine

Brain: RP2350
The same: Within half a semitone
LOOP: AUTO, or 1 to 64 steps
PATIENCE: 1 to 32 loops
SAME: None to a quarter of the loop
IN read: 0.5 ms after each clock