Routing and buses on a digital console: understanding the signal path

What is an audio bus?

An audio bus is a shared path where you sum several signals to process them together and/or send them to one or more destinations. The most telling metaphor: the highway of sound. Each channel (vocals, guitar, guest mic, playback track) is a car joining a highway (the bus) to reach a destination (physical or virtual output). This addition is mathematical: you sum signals at a specific point in the path (tap point), then apply EQ, compression, limiting, delay if needed, before sending the bus output to the chosen outputs.

The console offers several “highways”, each for a specific use. Understanding these types helps you make the right choices in console routing:

• Master bus (Main L/R or L/C/R): the main PA output. Most channels are sent there, directly or via groups. It is your tonal and dynamic reference for the room.
• Auxiliary buses (AUX / Mix / Monitor): independent paths to create separate mixes: stage wedges, in-ears, sends to effects, recording, streaming, intercom, sidefills, wedges, etc. An AUX can be mono or stereo depending on configuration.
• Submix / Groups (Group, DCA/VCA for control): grouping families (drums, backing vocals, orchestra) to process or control them with a single fader. A Group carries audio (you can insert EQ/comp); a VCA/DCA does not carry audio but controls the faders of the assigned channels without changing the routing topology.
• Matrix (mix matrix): one or more mixes of mixes. You can sum LR + sub-bass + announcements + talkback to create a specific send (balcony, foyer, delay line, recording, broadcast), with its own processing and level, independent of LR.

Two essential notions govern how you use buses: pre/post (the tap point relative to the channel fader) and stereo/mono. In pre-fader, FOH fader moves do not affect the monitor mix (ideal for musicians); in post-fader, they follow your FOH balance (ideal for time-based effects such as reverb and delay). In stereo, channel pan affects the perceived position; in mono, you prioritise intelligibility and robustness.

Routing explained simply

Visualise the flow as a logical chain: Inputs → Channels → Buses → Outputs. Each link has a precise role and dedicated settings:

1. Inputs: microphones, DIs, instruments, players. They hit the preamps (gain setting, phantom power if needed), then are converted to digital. A good practice is to aim for peak level around −12 to −6 dBFS, with an average level near −18 dBFS to preserve headroom.
2. Channels: correction (HPF to clean up low end, EQ to sculpt), dynamics (gate for hygiene, compressor for stability), delay if needed (time alignment or effect). The channel then distributes its signal to different buses according to your needs (AUX, Groups, LR).
3. Buses: sum several channels. A bus can be pre-fader (independent from FOH level) or post-fader (follows your FOH balance). Groups allow shared processing for families; matrices aggregate buses to feed zones or specific destinations, each with its own EQ and limiter.
4. Outputs: physical (XLR, jack, AES/EBU), network (Dante, AVB, AES50) or virtual (USB, recording card). You “patch” a bus (or a matrix) to one or more outputs. The patch links an internal signal (bus, direct out) to a real or virtual connector.

Key idea: you generally avoid sending a channel directly to an output (except specific cases such as a recording direct out). You go through a bus, sometimes a group, then a matrix, and finally an output. This hierarchy keeps the mix predictable and simplifies troubleshooting.

A frequently overlooked point: the tap point (pre-EQ, post-EQ, pre-fader, post-fader, post-on). Choosing the right tap point guarantees that the bus receives exactly what you want (for instance, sending in-ears a post-EQ but pre-fader signal, so they benefit from EQ without being affected by FOH moves).

Setting up routing on a digital console

Each brand has its own terminology, but the logic remains the same. Here are some concrete reference points for three very common consoles: Behringer/Midas X32, Allen & Heath SQ and Yamaha TF. The labels below are generic and may vary slightly depending on firmware versions.

Example 1: Behringer/Midas X32 (and derivatives)

• Sending to monitors (AUX/Mix): press Sends on Fader, select the desired monitor bus (e.g. Mix Bus 1). Raise the faders of the channels you want to send. Choose Pre-Fader for a mix independent from FOH, or Post-Fader if you want FOH balance to affect the monitors. Remember to link two buses to create a stereo in-ears bus, then adjust channel pans.
• Sending to FX: use a dedicated bus (e.g. Bus 13–16) patched to an internal FX slot. Send your channels to this bus in post-fader mode (the standard for reverbs). Return the effect on “FX Return” channels and avoid sending those returns back to the same FX bus to prevent feedback loops.
• Broadcast send: create one or two dedicated stereo buses (e.g. Bus 9–10) in post-fader mode but with dedicated processing (softer EQ, slower compression). Route this bus to a Matrix if you need to add other sources (room mics, announcements), then patch the matrix to the output (USB card, XLR, AES50).
• Output patching: in the “Routing” page, assign each Bus/Matrix to the XLR Outs, USB Out, AES50, etc. Check the banks (Out 1–8, 9–16) and tap points (pre/post processing). Keep 6 dB of headroom on your buses and matrices to avoid cascading clipping.

Example 2: Allen & Heath SQ

• Monitor mixes: put a channel in Mix mode (press the “Mix” button of a bus). The faders become the send levels to that bus. Set pre/post in the bus menu. Each Mix can be mono or stereo; for in-ears, prefer stereo and manage panning at channel level.
• Effects: patch a bus to an FX Send, load a reverb/delay and return it to an FX Return (stereo). Post-fader is recommended to keep musical coherence when you pull an instrument down in LR.
• Broadcast/Record: use a dedicated Group or stereo Mix, then route it to USB/Card and/or the Matrix. The I/O page handles patching visually (Local, SLink, USB, I/O Cards). Tip: keep a higher HPF (60–80 Hz) on the broadcast bus to limit rumbles.

Example 3: Yamaha TF

• Aux/Monitor: select the AUX bus then “Sends on Fader”. The Mix Sends are adjusted channel by channel. Choose pre/post in the bus configuration. Name mixes by musician (Vocal IEM, Drummer Wedge) to keep things clear.
• FX: send to the internal FX (REV, DELAY). The return comes back on dedicated stereo channels. Post-fader in most cases. Adjust reverb pre-delay so it does not smear vocal articulation.
• Matrix: sum LR and other buses to feed zones (balcony, foyer) or a streaming feed. Final patching is done in the “Output Routing” page. Use gentle limiters on each zone matrix to prevent accidental overshoots.

Golden rule: name your buses (Singer In-ears, FX Vox Reverb, Broadcast, Sub-bass, Foyer) and colour-code them. You will avoid most live mistakes and work faster. Document your patch plan and keep it in your show folder.

Stereo, mono, group, matrix buses: differences and uses

Choosing the right type of bus determines how you handle mixing, monitoring and distribution. The table below summarises typical use cases and precautions. Keep in mind that “stereo vs mono” is not a question of quality but of purpose: stability and punch in mono, image and space in stereo.

• Monitors: mono buses for wedges; stereo buses for in-ears (pan is crucial to “open up” the musician’s mix and reduce the required overall level).
• FX: dedicated stereo buses post-fader feeding reverb/delay, returns on “FX Return” channels. High-pass around 120 Hz on the return to preserve clarity.
• Groups: apply EQ/comp/glue to a family (e.g. drums), then send the group to LR. Bus compression adds cohesion; avoid excessive gain reduction that would crush dynamics.
• Matrix: create variations of your mix for zones/streams with their own limiter/EQ. Add a slight tilt EQ to compensate for foyer or balcony acoustics.

Common routing mistakes to avoid

Loops and double sends

• Group + Channel to LR: if a channel is sent both to a Group (itself routed to LR) and directly to LR, you are doubling the same signal (risk of +6 dB). Solution: send the channel only to the Group, and route the Group to LR. Also check phase if different processing is applied.
• FX returned to its own Send: creates an effects loop and runaway levels. Solution: make sure the FX Return is not sent to the corresponding FX bus and put FX returns in “solo safe”.
• Matrix fed by LR + Group already in LR: double counting. Solution: define precisely what feeds the Matrix (for example LR alone, or specific Groups not routed to LR) to avoid redundancy.

Hidden clipping

• Upstream clipping: a clipping preamp will remain distorted even if you pull the fader down. Solution: watch PFL levels on inputs and adjust gains; aim for −12 to −6 dBFS peaks.
• Gain stacking: sends too hot into buses, then buses too hot into matrices. Solution: adopt consistent gain staging: clean inputs, faders near 0 dB, buses/matrices leaving some headroom. Put protection limiters on matrices feeding public zones.

Tips to check your audio flow

• Solo PFL/AFL: PFL to check the input before the fader; AFL to listen to the sum of a bus with its processing. Use both to track down a stray signal.
• Oscillator/test tone: send a 1 kHz tone at −18 dBFS to LR, buses and matrices to check that levels are consistent up to the physical outputs. Also test pink noise to verify zone EQ.
• RTA/Bus meters: a “silent” bus still showing level often means an FX return or forgotten source. Temporarily zero the sends to isolate the culprit.
• Systematic naming & colouring of channels and buses: readability prevents mistakes under pressure. Use conventions (01 Kick, 02 Snare, BUS 1 Vox IEM, etc.).
• Patch plan: write down on one sheet the mapping Input → Channel → Bus → Matrix → Output. It is your anti-bug weapon and your handover tool for other engineers.

Conclusion

Mastering routing and audio buses on a digital console means taking back control of the clarity, dynamics and distribution of your mix. By visualising the path Input → Channel → Bus → Matrix → Output, choosing the right type of bus for each need (monitors, FX, groups, zones) and keeping disciplined gain staging, you get a mix that is clean, predictable and easy to replicate from one venue to another. This method reduces surprises, speeds up soundchecks and secures your chain all the way to network or USB outputs.

To dive deeper into global level control without touching the audio path, check out our guide VCA in audio.

FAQ

Practical recap

• Monitors: pre-fader AUXes (mono for wedges, stereo for in-ears); use pan to open up the IEM mix and lower perceived level.
• FX: dedicated post-fader AUXes, returns on stereo channels; filter low end on the return and avoid sending the return back to its own FX bus.
• Groups: shared processing for a family, route the group to LR (avoid double-routing channel→LR + group→LR); prefer VCA/DCA when you do not want to reprocess the audio.
• Matrix: spin-offs of the main mix (zones, streaming) with dedicated processing and limiter; adapt EQ by destination (balcony, foyer, recording) without disturbing LR.
• Gain staging: clean inputs, faders near 0 dB, headroom on buses and matrices; target around −18 dBFS average level and keep 6 dB of safety.
• Control: PFL/AFL, oscillator, RTA, up-to-date patch plan; name and colour everything for readable, sharable console routing.