Last Updated 3 days ago
An audio mixer is a device or software system that combines and controls audio signals, sending them to one or more outputs. It lets an operator balance sources, route them to different destinations and, where provided, apply processing. In equipment discussions, the term describes the mixing system, rather than the person working as a production sound mixer or re-recording mixer.
Channels, Buses and Outputs
An input channel handles a source such as a boom microphone, wireless receiver or playback feed. A bus collects signals from selected channels. The main mix is one possible bus, while auxiliary buses can create additional mixes for headphones, monitoring or effects. Output connections then carry the chosen signals to other equipment.
This structure explains why a mixer can send different versions of the same sources to different destinations. The camera may receive a useful dialogue mix while an interviewer hears a different headphone balance. A mixer is therefore more than a volume control shared by several microphones: its routing determines what each destination receives.
Input Gain and Fader Level
Input gain prepares the incoming signal for the mixer's working range. The channel fader usually controls that channel's contribution to a particular mix later in the path. Turning down a fader does not necessarily prevent the microphone preamp or another earlier stage from overloading.
Set up each source at its expected performance level and leave room for louder moments. Then establish the mix balance. A quiet voice may need a different input setting from a strong line-level receiver output. Read the input mode and metering rather than copying a neighboring channel's knob position. The controls may look alike while receiving very different signals.
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More Than One Mix
An auxiliary send takes a portion of a channel into another bus. A pre-fader send is taken before the relevant fader, so changing the main balance need not change that auxiliary feed in the same way. A post-fader send follows the fader and is often useful when an effect should track the source's level.
Exact routing varies. “Pre-fader” does not automatically mean before every filter, mute or processing stage. For a critical headphone or camera feed, consult the signal diagram and test what happens when a channel is lowered, muted or processed. A route should be understood before it is relied upon during a take.
Listening and Metering
Solo and cue functions help examine individual signals without necessarily changing the main output. PFL generally means pre-fader listen; AFL means after-fader listen. These functions can make troubleshooting faster, but the point being monitored matters. An input meter, a bus meter and a camera's record meter are checking different parts of the chain.
Imagine a microphone appears healthy on the input meter but is absent from the camera track. Possible causes include a closed fader, missing bus assignment, output routing or a camera input mismatch. Following the signal stage by stage is more productive than raising every control. Monitor the receiving device or test recording as well as the mixer's local headphone path.
Mixing Is Different From Recording
Some mixers include recording and computer-interface functions; others require a separate recorder. Even a mixer-recorder may offer different choices for which signals are written to files. A mixed track combines sources, while isolated tracks preserve individual channels for later editorial decisions.
For example, a scene with a boom and two lavaliers may benefit from a working dialogue mix plus separate microphone tracks. Confirm the record routing and whether each isolated track is taken before or after particular controls. Moving a fader should not unexpectedly alter a track intended to remain independent of the live mix. Record and replay a test instead of relying only on a menu label.
Analog, Digital and Software Mixers
An analog console performs its mixing through analog circuitry. A digital mixer handles audio through digital processing, commonly with configurable routing and recallable settings. A software mixer runs within a workstation or other application. Their interfaces differ, but channels, buses, gain structure and monitoring remain useful concepts across them.
A control surface may resemble a mixer while only sending commands to software. Likewise, having many physical faders does not establish how many separate audio inputs or recording tracks a system supports. Choose equipment by the required routes, sources, monitoring and recording workflow. On set, a clearly labeled, tested configuration is more valuable than unused features that nobody has checked.
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