BeachTek DXA-MICRO PRO+ Operating Manual page 16

How to Setup Audio Bracketing
Audio Bracketing is a simply a technique of setting a secondary channel
at a lower level to use as a backup in case the primary channel gets
blown out from an overly hot signal. This can be used anytime a single
mono mic is being used with the adapter. It is very easy to do:
1) Plug the mic into any input which will be the primary channel.
2) Set the OUTPUT switch to M for MONO.
3) Adjust the primary channel level as usual.
4) Adjust the other secondary channel at a somewhat lower level
between 10 and 20dB.
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