thump

20 HP · drums

The rack's drums: an 808-style kick that plays basslines from V/OCT, a snare that turns into a clap, and a hat that runs from six detuned squares to an industrial clang. Patch the rest of your rack into IN and every kick pushes it down, for as long as the kick booms, so the whole case pumps. GRIT drives, folds and crushes the drums, and every trigger is velocity. Rabbits thump the ground to warn the warren. This one keeps time.

The THUMP panel: black, a black rabbit's head in gold halftone dots, lit from above so only its ears, brow and muzzle catch the light, its eyes two dark hollows either side of V/OCT. White labels: TUNE, DECAY and SNAP down the left for the snare, TUNE, DECAY and METAL down the right for the hat, PUNCH, PITCH and BOOM between the ears, DUCK and GRIT, then the jacks. thump at the top, daylight noise at the bottom.

Turn a knob: drag it, roll the wheel over it or use the arrow keys; a double click puts it back. Press a trigger jack (KICK, SNARE, HAT) for a hit, Shift for an accent.

The drums, and a pad or an arpeggio into IN L/R so you hear the pump, all made in the page.

example patches

The module's own engine, running in your browser: the firmware's three voices, GRIT, the velocity detectors and the duck, ported from its C and checked against it bit for bit, with a model of the analog path the kick pushes down.

The kick

A sine that starts high and falls into its note, the way an 808's kick does, with a click on top. With a sequencer in V/OCT it plays the bassline.

PITCH: the note it falls to, 30 to 120 Hz, on the big knob.
V/OCT: right under PITCH, a volt an octave on top of it. The pitch follows it while the kick rings, so slides slide.
PUNCH: how far it falls and how hard it clicks. Low, a soft round 808; high, a sweep from fifteen times the note in a few milliseconds.
BOOM: the decay, 40 ms to 3 s. Long, and the kick is a bass.

Three kicks from the engine: PUNCH up and BOOM short; the middle; BOOM long.

Snare and hat

Snare · left

Two tuned tones that drop a little as they strike, and a band of noise. SNAP goes from tone to noise, a fat thud to a crack; past three quarters it's a clap, three or four quick bursts of noise, then the tail. TUNE moves the tones and the noise together; DECAY sets how long it rings.

Hat · right

The 808's hat: six square waves at odd ratios through a band-pass. METAL narrows the band, then rings the squares against each other into an industrial clang. TUNE moves all six an octave either way; DECAY runs from closed to open.

The duck

Every kick pulls IN L and IN R down at once, holds them a moment, then lets them swell back over about as long as the kick booms: short kicks flutter, long ones heave. The path is analog end to end: nothing patched into IN touches a converter.

DUCK: how far down, up to 36 dB at a normal hit, near silence. Most of the travel is in the top half.
IN L and IN R: what gets ducked. IN R is normalled to IN L, so a mono source comes out on both.
OUT L and OUT R: the ducked pair with all three drums mixed in.
KICK, SNARE, HAT out: each voice alone. Patched, it leaves the OUT L/R mix; patch all three, even to nothing, and OUT L/R are only the ducked pair.

A steady tone through IN L, at OUT L, against four kicks: BOOM short, then long.

Velocity

There's no accent jack: a trigger's voltage is its velocity. The firmware finds each trigger's edge, waits for the top, and plays the hit at that height, within a millisecond.

1 to 5 V: softer, in proportion: 2.5 V is half as loud, and a soft kick ducks less. A hit starts above 1 V and re-arms below 0.5 V.
5 V: a normal hit, most sequencers' trigger. The levels on this page, and DUCK's 36 dB, are at 5 V.
5 to 10 V: an accent: up to 2.6 dB louder, a deeper sweep on the kick, a soft clip on every voice and a deeper duck. 10 V is a full accent.

Grit

One knob through three stages, on the drums only. The ducked path stays clean.

Drive: the first third, up to nine times into a soft clip. Kicks pound and flatten.
Fold: through the middle, what goes past full scale folds back on itself, so a kick's sine barks and a snare frays.
Crush: the last part, down to five bits and a 3 kHz sample rate.

The panel

A black rabbit lit from straight above, in a halftone of exposed gold, its eyes two dark hollows either side of V/OCT. The outputs are knocked out of white blocks; everything else is an input.

The name is from Watership Down, where the thump is the first thing a young rabbit learns to trust.

Inside

Drag to look around. Nothing on the board has been soldered yet.

Specs

Format

Width: 20 HP
+12 V: about 95 mA (the design's estimate)
−12 V: about 20 mA
+5 V: not used; 10-pin header
Panel: 1.6 mm FR4, ENIG gold through black mask
Controls: 11 knobs, no switches

I/O

Triggers in: KICK, SNARE, HAT: 0 to 10 V, the velocity; 143 k
V/OCT: the kick's pitch, 1 V an octave, −2 to +8 V
Audio in: IN L, IN R, 100 k; IN R normalled to IN L
Voice outs: KICK, SNARE, HAT; patched, it leaves the mix
Mix out: OUT L, OUT R: the ducked pair with the drums
Out level: about 10 Vpp into 1 k (TL07x)

Engine

Brain: RP2350, the voices at 48 kHz
DACs: 2 × PCM5102A on one I2S clock
Duck: 2 cells of an SSI2164, set by a filtered PWM voltage
Inputs: knobs and V/OCT through a 16-way mux; each trigger its own converter input, at 48 kHz
Firmware: over USB-C or the debug header, on the back

Nothing's for sale yet.

THUMP is designed and its firmware builds. Nothing has been soldered, so the numbers here are the design's, not measurements, and there's no date.

hello@daylightnoise.com