Mutable Instruments Marbles — Antumbra Black Panel

Build and provenance — please read: This is a DIY build, not a factory unit, fitted with an Antumbra black panel rather than the original Mutable panel. The PCB was fabricated from Émilie Gillet's open-source design files, with SMD components machine-placed by JLCPCB. Through-hole assembly, testing and calibration done by hand.

What it does:

A source of random gates and voltages with an unusual amount of control over what kind of randomness comes out. Three gate outputs and three CV outputs, split into two sections.

The t section — random rhythm: runs its own internal clock with adjustable rate and V/Oct CV input, or locks onto an adjustable multiplication/division of an external clock. A range button multiplies or divides by a further factor of 4. There's a rhythm follower that latches onto uneven clock divisions and rhythmic patterns. The regular clock is then perturbed by a process simulating a player trying to follow a click and catch up on their own errors — dial it anywhere from perfect accuracy to complete chaos.

The X section — random voltages: three outputs that can all follow the panel settings, or react in opposite ways to each other. The STEPS knob is central here — the first half of its travel produces slewed voltages, rounding every step smoothly at minimum. Plus an auxiliary slow-fluctuating random voltage output.

DEJA VU — the reason people keep this module: increases the probability of replaying past material until the output locks into a loop, then keeps going and starts randomizing the order of that loop. Applies to the rhythm, the voltages, both, or neither. Loop length adjustable from 1 to 16 steps. You can record an external CV into the DEJA VU loop in place of the internal random voltages.

Programmable quantizer: scales are taught by playing a short jam in the target scale — Marbles works out which notes matter and quantizes to them.

External processing mode: samples voltage present on the SPREAD CV input whenever a random value is needed for one of the X outputs, letting you randomize material from a conventional sequencer.

Specs: 18 HP · +12V 80mA / -12V 20mA · all inputs 100k impedance, DC to 3.2kHz · max input clock rate 1kHz on t, 8kHz on X · CV outputs -5V to +5V at the largest setting, gates 0V to +8V · input CV range -5V to +5V · 12-bit CV capture, 14-bit DAC with software calibration