For a simple DX/MX/FX house layout, I give every stage one normal output: source track to its submix, then submix to Stereo. A route like that is easy to audit at a glance. It's an editorial recommendation, not a FlexBus limit.
Resolve supports multiple outputs and sends. Trouble starts when parallel paths rejoin unintentionally, such as VO feeding both DX and Stereo while DX also feeds Stereo. The voice then arrives twice, and the mix gets louder for no good reason.
The Fairlight signal flow in plain English
A track holds clips. A bus sums the output of one or more tracks or other buses. That summed signal gets its own channel strip, so you can change the level, EQ, dynamics, plug-ins, panning, automation and destination for the whole group at once.
| Path | What it does | Use it when |
|---|---|---|
| Track, then Stereo | Sends the track directly to the final output bus | The timeline is small and you do not need group processing or stems |
| Track, then DX/MX/FX, then Stereo | Routes related tracks through a controllable submix | You want one fader, shared processing, automation, or a deliverable stem for each family |
| Track, then normal output plus Bus Send, then VERB | Creates a second, parallel path | You want reverb, delay, a cue mix, or another effect without replacing the dry route |
Resolve 21 uses FlexBus. A bus doesn't carry a permanent “main,” “submix” or “aux” type; its role comes from what feeds it and where its output goes. The Resolve 21.1 Reference Manual documents track-to-bus, bus-to-bus, bus-to-track, output and send assignments, and every new timeline starts with one default bus called Bus 1. The active paths are the source of truth, not the name printed on a bus.
Build a clean DX, MX, and FX bus layout
1. Name the source tracks before touching routing
Rename generic tracks such as A1 and A2 by role: VO 1, Boom, Lav, Music, SFX, Ambience. A routing matrix full of anonymous track numbers is miserable to diagnose later. If the dialogue is already edited, clean the clips first; our Remove Silence guide covers the fastest safe workflow.
Check the track format too. Most individual microphones belong on mono tracks. Music and many effects arrive as stereo. Pick the bus format for what the group needs to deliver, not for whatever format the first clip you see happens to be.
2. Create and name the buses
Open the Fairlight page and choose Fairlight, then Bus Format. Rename the default Bus 1 to Stereo so nobody has to guess which bus is the final mix, then add only the submixes you need. DX, MX and FX make a practical starting layout. Add VERB only if you need a shared parallel effect.
- Stereo: the final two-channel mix.
- DX: dialogue and voice-over. A mono bus can suit a mono dialogue stem; stereo is also valid when your delivery or processing calls for it.
- MX: music, usually stereo.
- FX: effects and ambience, usually stereo for web and standard stereo delivery.
- VERB: a stereo auxiliary return for reverb or delay.
Don't copy those formats blindly into a surround or broadcast project. The delivery specification wins. Blackmagic also documents adaptive tracks for unusual channel layouts, but a normal YouTube video or course lesson doesn't get better because its routing diagram got more complicated.
3. Assign every source to one submix output
You can assign routing in the Mixer or open Fairlight, then Bus Assign. In the Mixer, open the three-dot Mixer Options menu to show Bus Outputs if that row is hidden. Then send every dialogue track to DX, music tracks to MX and effects tracks to FX.
Bus assignments can be additive: giving a track DX doesn't necessarily take it off Stereo. After assigning a source to DX, inspect Bus Outputs or Bus Assign and remove the direct Stereo route if both paths reach the same destination by accident. My house path is VO 1 > DX > Stereo. A deliberate parallel route is fine, as long as you know why it exists and where it ends up.
4. Route the submix buses to Stereo
Select the DX, MX and FX bus channel strips and add Stereo in their Bus Outputs. Now play a section that contains every category. The source-track meter should move, then its submix meter, then the Stereo meter. If one stage goes quiet, the fault sits immediately upstream of that meter.
Bus Output vs Bus Send: the difference that prevents doubling
A Bus Output is the normal destination. A Bus Send is an additional feed. That distinction matters more than whatever names you gave the buses.
For shared reverb, keep VO 1’s normal output on DX. Add VERB under Bus Sends, put the reverb plug-in on the VERB bus and route VERB to Stereo. Set the reverb plug-in on VERB to output only the processed signal: in Fairlight FX Reverb, use Dry/Wet at 100%. Then balance the return with the send level or the VERB bus fader. The dry dialogue path stays intact, and the processed return runs beside it in parallel.
Sends are post-fader by default. A post-fader send follows later moves on the source fader, which is usually what reverb wants: lower the voice and its reverb falls with it. A pre-fader send stays independent of the source fader; the manual points to cue and ADR feeds, and it suits other monitoring feeds too. Pick deliberately; neither mode is universally “more professional.”
Processing that should hit the entire group belongs on the submix, not on an aux return. For example, use the Fairlight dialogue EQ workflow and the dialogue compression guide to shape DX as one voice. Save sends for reverb or delay that has to sit beside the dry sound.
Verify the route before mixing
Run these short tests before you insert another plug-in. They expose routing errors faster than staring at a large mixer.
- Meter test: play one source at a time and follow its meters from track to submix to Stereo.
- Mute test: mute DX to check the dry dialogue path while music and effects keep playing. If dialogue tracks also send to VERB, their reverb can still reach Stereo through that separate return; check or mute VERB separately. Repeat the dry-path check for MX and FX.
- Unity test: bypass bus processing, set the relevant faders to unity and compare the rebuilt route with the original. A sudden jump in level usually means a duplicate direct path is still active.
- Speaker/device test: if track, submix and Stereo meters all move but the speakers stay silent, stop rebuilding buses. Check Bus Outputs, Control Room or monitor selection, Resolve audio I/O, the operating-system output device and any required patching.
Keep routing, monitoring and delivery apart in your head. If the Stereo meter moves, the track-to-bus chain is passing signal. Silence after that point belongs to Bus Outputs, Control Room or monitor selection, Resolve's audio I/O and output-device configuration, operating-system audio, or patching. And whatever you pick for monitoring doesn't select the Deliver output.
Export the full mix and stems on the Deliver page
Open Deliver and choose an audio-capable preset or Audio Only. The Audio Only preset starts on MXF OP-Atom with 16-bit Linear PCM, so change it if the handoff should be a WAV file: Wave with Linear PCM is the common lossless choice, and 24- or 32-bit output is available. The required bit depth and channel layout still come from the client or platform specification.
- Choose Single Clip so every output covers the same render range.
- Under Audio, set Output Track 1 to the final Stereo bus.
- Click the plus button to add DX, MX and FX as additional Output Tracks when the job calls for stems.
- Confirm each displayed format, Mono, Stereo, 5.1 or another layout, before you queue the render.
- Render a short test, reimport it into a blank timeline and check the start time, duration, channel count and content.
The Deliver page can output several buses in the same render job. That's different from choosing “All Timeline Tracks,” which prints timeline tracks rather than the processed submix structure. If the stem must carry the EQ, compression, automation and other processing on DX, export the DX bus. I'd also leave Audio Normalization off for stems unless the delivery sheet asks for it: it's set per output, so each stem would get its own gain and the stems would no longer add up to the mix.
Real broadcast deliveries can demand empty channels, multiple language mixes or a precise interleaved layout. A useful community routing example for an eight-channel broadcast file shows why the bus names, formats, Output Track order and the “Render one track per channel” choice have to follow the delivery sheet rather than a generic preset.
For a normal web upload, export the final Stereo bus and check its loudness after all submix processing. Targets and the measurement workflow are in our Fairlight LUFS and audio levels guide. For codec and file settings, use the separate DaVinci Resolve audio export guide.
Fairlight bus routing troubleshooting
The track meter moves, but the bus is silent
Check the track’s Bus Outputs as well as its sends. Make sure the playhead is over an audible clip, the destination bus isn't muted and the source fader or automation hasn't pulled the signal down. Then open Bus Assign, which starts in List view, and look for the bus number in that track's Bus Outputs column. In Icon view the same assignment shows as the bus number followed by “o” for an output or “s” for a send.
The submix moves, but Stereo is silent
If the submix meter moves but Stereo doesn't, inspect the submix's Bus Output, fader, mute and automation, plus the mute state on Stereo itself.
If Stereo also moves but the speakers are silent, routing has passed the meter test. Look at Control Room or monitor selection, Bus Outputs, Resolve audio I/O, the OS output device and patching instead of recreating the submix.
The full mix is louder after adding submixes
The source tracks probably still feed Stereo directly while also feeding submixes that feed Stereo. Remove the direct Stereo output from those source tracks. Be careful with Assign All in Bus Assign, too: with Stereo selected, it assigns every track, Sub and Aux to that bus and brings the doubled path straight back. Don't fix a duplicated route by arbitrarily lowering the master fader; repair the signal flow.
The stem is missing bus effects
You exported timeline tracks or the wrong bus. Choose the processed DX, MX or FX bus in Output Track. If an effect lives on a separate aux return, decide whether the delivery specification expects that return folded into the stem, delivered on its own, or present only in the full mix.
The export is mono when the mix should be stereo
Inspect the format at every stage: source track, submix, final bus and the selected Output Track. One mono bus in the chain can collapse the result. Change formats on purpose in Bus Format, then confirm the Deliver dropdown reports the channel layout you expect.
Does Fairlight bus routing require Resolve Studio?
No. Standard FlexBus routing, buses, sends, channel mapping, mixer processing and stereo stem workflows are all available in DaVinci Resolve Free. Studio adds tools and formats that may matter for advanced immersive work, and the manual lists the immersive bus formats as Studio only. You don't need Studio to build a clean DX/MX/FX mix.
This guide targets DaVinci Resolve 21, and its routing names match the 21.1 Reference Manual. The current Fairlight overview confirms the channel-strip processing model, with FlexBus in place of fixed aux, sub and main buses. Menus can shift, so anchor on the documented names: Bus Format, Bus Assign, Bus Outputs, Bus Sends, Control Room and Output Track.
A routing checklist I would trust at delivery
- Every source track has a clear name and the intended mono, stereo or multichannel format.
- Every source has one normal output path, unless duplication is deliberate and documented.
- DX, MX and FX all reach the final Stereo bus.
- Aux buses such as VERB also reach Stereo and carry only the intended parallel return.
- Each mute test checks the intended dry path, with parallel effect returns checked separately.
- The Stereo bus and every requested stem are selected explicitly in Deliver, under Output Tracks.
- A rendered test has been reimported and checked outside the live routing session.
If every bus meter moves and the speakers still give you nothing, work through the no-audio device and monitoring checklist before you touch the routing graph.
Fairlight bus routing FAQ
What is a bus in DaVinci Resolve Fairlight?
A bus is a signal path that sums one or more tracks or other buses into a new mixer channel. It lets you control, process, monitor, route or export those sources as one group.
Should every audio track go to its own bus?
No. Create buses for useful groups and deliverables. Several dialogue tracks can share DX, music tracks can share MX and effects can share FX. A tiny project can route its tracks straight to Stereo.
What is the difference between a bus output and a bus send?
A Bus Output is the track’s normal destination. A Bus Send is an additional parallel feed with its own level and pre- or post-fader behavior, and it's post-fader by default. Sends are commonly used for shared reverb, delay or cue mixes.
Why does audio get louder after I route it to a submix?
The source is usually reaching Stereo twice: once directly and once through the submix. Remove the direct Stereo output from the source so it travels only through the intended submix.
How do I export dialogue, music, and effects stems?
Route those families to named DX, MX and FX buses. On Deliver, use the plus button under Output Tracks to add each bus, verify its channel format, render the same range and reimport the files to check that they line up.
Can I route one Fairlight track to more than one bus?
Yes. FlexBus lets a track output to up to 10 buses and send to 10 more, and buses can feed other buses up to six levels deep. Use parallel paths only when the design requires them, and trace every path to its destination; unintended routes that rejoin can raise level or bypass group processing.
