What is a Mix Bus?
A mix bus is a way to send or “route” one or more selections of audio to a particular place. Some common destinations or places to route audio are aux sends, subgroups, and your main L/R mix. You will route your desired channels or audio to the bus of your choice (Aux Send, Main L/R, VCA, etc.) and then feed that signal to the destination you wish by turning up your faders or knobs for those channels within that bus.
Mix Bus is a term used in the live sound and recording worlds and is commonly associated with output channels/busses as discussed above. Being able to adjust multiple sources or channels with a single “group” fader is one of the bigger advantages to having multiple busses at your disposal.
Here is a video explaining how to use Subgroup (or bus) on a DL Series mixer.