Sound Ministry Series Part 8 - The AUX buses

So, what's a bus? Well, it's something that gets you from one place to another! On a mixing console, when we see the word BUS, that's just what it is - a routing device to get the signal from one place to another.

The AUX (which stands for auxiliary, meaning secondary or additional) buses are used to create a second, third, fourth or even fifth mix (with the front of house mix being first) that can be used for stage monitors, recording of sermons and worship, cry-rooms, broadcast, etc.

Each channel should have knobs labelled AUX1, AUX2, etc. These are used to control the level of that individual channel in the AUX mix. Somewhere on the far right of the desk should be other knobs or sliders also labelled AUX1, AUX2, etc. which are used to control the overall volume of the AUX mix. Near the top right of the desk, either on top or on the back, there should be outputs for each AUX bus for plugging in a cable to take the signal, well, anywhere you want!

Here are some worked examples:

Recording the sermon

Plug your recording device, like a computer soundcard or a tape recorder, into their AUX1 output. Increase the volume of the overall AUX1 volume (the one on the right of the desk) to about halfway. Use the AUX1 control on the preacher's microphone channel to adjust the recorded volume. Your AUX1 bus is now your recording mix! You can add other channels to this mix by using their AUX1 controls.

This idea is the same for a cryroom. Just plug the cryroom feed into the AUX1 output.

Stage Monitors

Remember that each AUX bus can provide you with a separate monitor mix (depending on how many monitors you have). For now, let's use AUX2 and AUX3 for vocal and instrument monitors respectively (remember that AUX1 is our recording bus).

Plug your monitor sends into their respective AUX outputs on the mixer. Adjust the volume of each AUX mix to about halfway. Ask the band to play, and let them help you to determine how much of each instrument or vocal needs to be added to each monitor mix. You can also walk up there yourself and take a listen, but that's going to involve a lot of walking back and forth! The vocal mix (AUX2) will need more vocals and less instruments, and the instrument mix will need the opposite, but still enough vocals to hear the words so they don't get lost!

Finally, always ensure that your AUX buses are "pre-fade". There should be a button on each channel allowing you to set your AUX buses to pre- or post-fade. If they are set to post-fade, any change you make to that channel in the main mix will also affect the monitor mix. For instance, you turn up the piano in the main mix and it also goes up in the monitor! Pre-fade allows you to maintain completely independent AUX mixes.

The only time you may want post-fade AUX buses is if you are controlling an effects unit from an AUX bus. If this is set to pre-fade, the sound from the effects unit will still be heard when you turn the channel down.

Remember, however, that if you have your AUX buses on pre-fade, the MUTE switch won't work on the AUX buses - i.e. you will still hear a "BOOM" on the monitors when someone unplugs even if the channel is muted - you will have to turn down the AUX buses separately.

Comment if anything's still unclear.

Next time: The PAN control