StemDeck × A³ Motion

At a glance

The drop comes. On deck A the vocal rises over the crowd and comes back down on the one. On the CDJ beside it the hi-hats circle the floor. The kick and the bass of both hold the ground. Two instruments did that, each on its own kind of source, and both landed on the same bar because they share one clock.

	Moves	How you play it
StemDeck	its own stems, one at a time	the action pads ORBIT, PING, RISE, SCAT on a stem, from the next bar
A³ Motion	the stereo channels (ST): a CDJ, a turntable, a laptop	a clip per channel; 3d, FREQ and Q pick the band that moves
The desk	nothing: it picks what plays	each channel’s INPUT knob: A to D for a deck, ST for the stereo input

• A deck is one source on the desk. Turn a channel’s INPUT to the deck’s letter and push. The channel’s fader, EQ and filter then act on the whole deck.

• A³ Motion does not move a deck. On a deck channel its screen says DECK A (or B, C, D) and it sends no movement for that channel. The stems move by StemDeck’s actions. A deck in Output: Stereo has no stems in the room: its channel is moved by A³ Motion like ST.

• One clock for both: see Who is the clock.

Why it works so well

• One moving part over a steady rest reads as a gesture; a moving full mix smears. Both instruments follow this rule: A³ Motion lifts one band out of a stereo channel, StemDeck lifts one stem out of four.

• At rest a stem sits all around the room, with the rest of its track. Only while an action runs does it come loose, then it goes back.

• The two never fight over a channel. A channel plays either a deck or its ST input; Motion moves only ST channels, StemDeck moves only its own stems.

• One beat. StemDeck’s actions start on the next bar of its own grid; A³ Motion’s clips count bars from the beat clock. With one clock for both, the bar lines agree.

Setting it up

You need StemDeck and A³ Core with the Beat Analyzer. For the stereo side you also need A³ Motion (the hardware, or its screen alone, by touch or mouse) and a player on an ST input. The A³ Mixer hardware is optional: the virtual desk and A³ Motion’s MIXER pages have the same controls.

1. The audio: StemDeck into A³ Core

On the Core itself there is nothing to wire: the engine connects deck A, and a user service keeps it running (Always running on the Core). A deck on another machine: StemDeck on another machine.

2. The desk: a deck on a channel

Turn the channel’s INPUT knob to the deck’s letter and push; push ST to go back to the stereo input. A deck plays on one channel at most: pushing it on a second channel puts the first channel back on ST. The rules are on the desk’s input selectors.

3. The clock

Pick one clock for the evening: Who is the clock. With no CDJs, StemDeck is the master:

1. Load a set and wait for the BPM (no beats before the analysis is done).

2. Press MASTER on the deck: its top bar reads LINK master: A.

3. On A³ Motion, tap the clock key to PIO. The BPM follows StemDeck.

StemDeck broadcasts on its own network; the Core must be in it (always, on one machine). Chain: Playing without CDJs. Ask before joining a venue’s Pro DJ Link (Trademarks and Pro DJ Link).

Your first set

Step by step, with a CDJ on ST and a deck beside it: First set.

The MOTION / STEMDECK key at the far right of each top bar switches between the two screens (workspaces).

StemDeck on another machine

Deck A runs on the Core. Every further deck can run on a machine of its own, a deck host, one deck letter per host. The shipped I/O map expects deck B from another machine; on the I/O page each deck’s source can be switched between Local StemDeck and AES67 stream (the I/O map).

A deck host sends its deck to the Core as one AES67 stream of 41 channels on the audio network (ports); the Core’s REC bus comes back on channels 1 and 2 for the recorder. Both machines need a cable between their second sockets (or a switch) and an address each on 192.168.9.0/24; the Core’s is 192.168.9.10/24. The Core receives the stream outside the PTP clock.

The deck host needs only the StemDeck package, no a3-core: it ships the deck’s sender and link map (one deck per instance). Set up once:

1. Tell StemDeck where Core is: ~/.config/a3/core (StemDeck on radla).

2. Give the machine’s second socket its address on the audio network.

3. Set the sample rate to 44.1 kHz before StemDeck starts; the AES67 streams carry 44.1 kHz.

4. Run the installer’s deck-host role and answer its three questions: the deck letter, the path latency (0 until you have measured it) and the audio socket. It starts the deck with its sender, link map and clock, and sets the panel to follow the workspace (what the role does). Without the role, nothing is linked and the deck is silent on the Core.

On a deck host with A³ Motion beside it, the panel follows the workspace in front, A³ Motion or the deck.

Troubleshooting

Symptom	What to do
The deck is silent on the desk	Is the channel’s INPUT on the deck’s letter (bracket over it) and the fader up? On the Core: deck A’s ports against the engine’s peers on the I/O page (I/O map). Elsewhere: is the AES67 stream announced and cabled, and is PTP locked?
A³ Motion says DECK A and nothing moves	Right: Motion does not move a deck. Tap an action on a stem in StemDeck, or put the channel on ST for Motion
A stem plays but doesn’t move	Stems move only while an action runs: tap ORBIT, PING, RISE or SCAT and wait for the next bar
An ST channel doesn’t move	3d down, the clip not playing, or FREQ and Q on a band where the track has little
No tempo follow	BPM shown? Deck playing as master? A³ Motion on PIO? Core on StemDeck’s network?
Movements a beat off the bar	StemDeck: CUE on the real first beat of a bar, GRID, SNAP
Stems stop after an audio-settings change	Set the rate before starting StemDeck; check that the AES67 stream is still announced on the audio network