Open the manual for almost any mixer or streaming audio app and you hit two words that stop beginners cold: “bus” and “aux send.” They sound abstract, but they are the whole reason a mixer can send one blend of sound to your viewers and a different blend to your headphones or a guest. Understand these two concepts and mix-minus, monitoring, and clean VODs all suddenly make sense.
What a bus is
A bus is simply a channel that combines multiple audio signals into one path. When you route your mic, your game, and your music to the “main” bus, the mixer sums them into a single stereo signal that goes to your stream. Think of a bus as a collection point — several inputs pour into it, and it outputs one mixed result. A mixer typically has a main bus plus several extra buses you can create for other destinations.
What an aux send is
An aux (auxiliary) send is a knob on each channel that controls how much of that channel gets tapped off and routed to a separate aux bus — independent of the main mix. That independence is the magic. You can have your voice at full volume on the stream (main bus) while sending only a whisper of it, or none at all, to a guest’s aux mix. Aux sends let one source appear at different levels in different mixes.
Common buses in a streaming setup
| Bus / send | What it carries | Goes to |
|---|---|---|
| Main / stream bus | Full show mix (mic, game, alerts) | OBS / encoder |
| Monitor bus | What you hear | Your headphones |
| Aux send 1 (mix-minus) | Everything except the guest’s own voice | Remote guest |
| Aux send 2 | Music-free feed | VOD / archive |
Why streamers need this
The classic problem aux sends solve is echo on calls. If you send a guest a mix that includes their own returning voice, they hear themselves delayed — a horrible echo. A mix-minus is an aux send that carries everything except that guest’s channel, so they hear you and the game but not themselves. That is impossible without aux sends feeding a separate bus.
Buses also protect your VODs. By routing copyrighted music to the stream bus but keeping it off a separate “clean” bus that records locally, you avoid muted or struck archives. And a dedicated monitor bus lets you turn a source up in your own headphones for troubleshooting without changing what viewers hear. Software mixers like virtual audio routers mirror all of this with virtual buses instead of physical knobs.
Buses in software audio routers
You do not need a physical mixer to use buses — virtual audio software recreates the same concepts with on-screen strips. A typical virtual setup has hardware input strips (your mic), virtual input strips (apps like Discord and your browser), and output buses labelled A1, A2, B1, and so on. You assign each strip to whichever buses should carry it, exactly like turning up an aux send on hardware.
A practical software routing map
Send your mic to the bus feeding OBS and to your monitoring bus. Send game audio to both as well. Send music only to your monitoring bus, not the stream bus, so a copyrighted track never reaches your VOD. Send a Discord guest to the stream but build them a return bus that excludes their own channel — that is your software mix-minus, killing the echo they would otherwise hear. Because everything is virtual, you can save the whole layout and reload it next session. The mental model is identical to hardware: a bus sums signals to one destination, and each strip’s assignment controls how much of it feeds each bus. Once buses click, advanced tricks become obvious — a separate clean recording bus, a karaoke-safe bus, a guest bus — all from the same handful of ideas. Learn the concept once and it transfers to any mixer, hardware or software, you ever touch.
FAQ
What is the difference between the main bus and an aux send?
The main bus is your primary output mix that goes to the stream. An aux send taps a variable amount of each channel to a separate bus for a different destination, so you can build an alternate mix without disturbing the main one.
Do I need aux sends if I stream solo with no guests?
Less so, but they are still handy for a clean recording feed or separate headphone monitoring. Once you add remote guests or want copyright-safe VODs, aux sends and multiple buses become essential.
Bottom line
A bus combines signals into one output; an aux send routes a variable slice of each channel to a separate bus. Together they let you build multiple simultaneous mixes — one for viewers, one for your ears, one for a guest without echo, one clean for archives. They are the foundation of any multi-source streaming audio setup.
