DMX Crossfader Logic
The DMX crossfader is a winner-takes-all system. At any given moment, exactly one deck is selected as the DMX master. Only that deck's lighting show plays. There is no blending or interpolation of DMX values between decks.
Four inputs combine to determine which deck wins:
- Crossfader position — the primary left/right signal
- Deck play state — whether each deck is actively playing
- Deck audio output level — the post-fader audio level (what actually comes out after the channel fader is applied), used as a tiebreaker in the center zone
- Playback duration — how long the deck has been playing, used as a final tiebreaker
Important
The channel fader (deck volume) influences master deck selection indirectly in the center zone — because it reduces the deck's audio output level, which is what the tiebreaker reads. However, the channel fader does not scale the DMX output values of the winning deck. DMX brightness is controlled separately by a global master dimmer. In the left and right zones, the channel fader has zero influence on deck selection at all.
Terminology
| Term | Meaning |
|---|---|
| Crossfader position | 0.0 = full left, 1.0 = full right, 0.5 = center |
| Left deck | The deck assigned to the left side of the crossfader |
| Right deck | The deck assigned to the right side of the crossfader |
| Playing | The deck is actively playing (transport running, track loaded) |
| Active | The deck has a track loaded, whether playing or not |
| Level | The deck's post-fader audio output level — the signal after the channel fader is applied. Turning the channel fader down lowers this value. Used only in the center zone. |
| Channel fader | The per-deck volume fader on the mixer. Affects audio level and therefore influences center-zone deck selection indirectly. Does not affect DMX output values directly. |
| Master deck | The single deck whose lighting show is currently driving DMX output |
| Disable crossfader | A setting that ignores crossfader position and forces center-zone logic |
Deck Side Assignment
In 2-deck mode:
- Left side = Deck 1
- Right side = Deck 2
In 4-deck mode:
- Left side = Deck 3 (if Deck 3 is playing and Deck 1 is not), otherwise Deck 1
- Right side = Deck 4 (if Deck 4 is playing and Deck 2 is not), otherwise Deck 2
Crossfader Zones
Center zone width: ±0.10 either side of 0.5
Master Deck Selection Logic
LEFT Zone (position ≤ 0.40)
Is the left deck playing?
RIGHT Zone (position ≥ 0.60)
Is the right deck playing?
CENTER Zone (0.40 < position < 0.60)
The crossfader position is ignored. The winning deck is determined by audio level, play state, and playback duration — in that priority order.
Step 1 — Find the loudest deck(s)
- Collect the current audio level of each active deck.
- Identify the highest level.
- Group all decks within a
0.05tolerance of that highest level → "tied decks"
Step 2 — Resolve ties among loudest decks
If only one deck is loudest:
If multiple decks are tied for loudest:
Find which of the tied decks are playing:
- Exactly 1 playing → that deck wins
- Multiple playing → the one playing longest wins (highest elapsed time)
- None playing → the tied deck with the lowest deck number wins
Step 3 — Fallback (no level data, or loudest deck is not playing)
Count how many decks are playing:
- Exactly 1 → that deck wins
- Multiple → the one playing longest wins (highest elapsed time); tie on time → lower deck number wins (1 beats 2, 2 beats 3, etc.)
- None → no master deck (show stops)
When the Crossfader Is Disabled
When the Disable Crossfader setting is enabled, the system ignores whatever position value is being received from the connected DJ software — whether from VirtualDJ, Traktor, or any other source — and forces the position to 0.5 (center) for every calculation.
This means:
- Center zone logic applies at all times
- The deck with the highest audio level wins
- If levels are tied, the playing deck wins; if both playing and tied, the longer-playing deck wins
- Moving the physical crossfader or sending crossfader automation has no effect on which deck drives the lights
This is useful when the user wants lighting to follow audio energy rather than crossfader position, or when using the crossfader purely for audio mixing without it influencing the lighting.
Full Decision Matrix
| Crossfader setting | Crossfader position | Left deck state | Right deck state | DMX master |
|---|---|---|---|---|
| Normal | ≤ 0.40 (left) | Playing | Any | Left |
| Normal | ≤ 0.40 (left) | Stopped / no track | Playing | Right (playing overrides position) |
| Normal | ≤ 0.40 (left) | Stopped, track loaded | Stopped / no track | Left |
| Normal | ≤ 0.40 (left) | No track | No track | None — show stops |
| Normal | ≥ 0.60 (right) | Any | Playing | Right |
| Normal | ≥ 0.60 (right) | Playing | Stopped / no track | Left (playing overrides position) |
| Normal | ≥ 0.60 (right) | Stopped / no track | Stopped, track loaded | Right |
| Normal | ≥ 0.60 (right) | No track | No track | None — show stops |
| Normal | 0.40–0.60 (center) | Playing, louder | Playing, quieter | Left (higher level) |
| Normal | 0.40–0.60 (center) | Playing, quieter | Playing, louder | Right (higher level) |
| Normal | 0.40–0.60 (center) | Playing, equal level | Playing, equal level, shorter time | Left (playing longer) |
| Normal | 0.40–0.60 (center) | Playing, equal level, shorter time | Playing, equal level | Right (playing longer) |
| Normal | 0.40–0.60 (center) | Stopped | Playing | Right |
| Normal | 0.40–0.60 (center) | Playing | Stopped | Left |
| Normal | 0.40–0.60 (center) | Neither playing | Neither playing | None — show stops |
| Disabled | Any (input ignored) | Playing, louder | Playing, quieter | Left (center-zone rules always) |
| Disabled | Any (input ignored) | Playing, quieter | Playing, louder | Right (center-zone rules always) |
| Disabled | Any (input ignored) | Playing | Stopped | Left |
| Disabled | Any (input ignored) | Stopped | Playing | Right |
| Disabled | Any (input ignored) | Neither playing | Neither playing | None — show stops |
Key Rules Summary
- Winner-takes-all — one deck drives DMX entirely, no blending.
- Playing beats stopped — in left/right zones, if the favored deck is stopped but the opposite deck is playing, the playing deck wins regardless of crossfader position.
- Level breaks ties in the center — the deck outputting the loudest post-fader audio signal wins. Because this is post-fader, turning the channel fader down reduces a deck's chances of winning in the center zone.
- Channel faders only matter in the center zone — in the left or right zones, the channel fader has zero influence on which deck wins. Only crossfader position and play state decide.
- Playback duration is the final tiebreaker — if levels are equal and both are playing, the deck that has been playing longer wins.
- Deck number is the last resort — lower number always wins (Deck 1 > Deck 2 > Deck 3 > Deck 4).
- Disabling the crossfader freezes position at center — all incoming crossfader data from any connected DJ software is ignored; center-zone logic applies permanently.
- Channel faders do not scale DMX output — they only influence deck selection indirectly via audio level. The actual DMX brightness of the winning deck is controlled by a separate global master dimmer and optional per-group dimmers.