Pre (yellow button on) is “pre fader” button off is “post fader.
That is the signal pick off point for the selected mix or FX.
Pre fade is picking the signal before the fader level changes, meaning changes
made to the main mix will not change the level send to the mix or FX.
Post fade is picking the signal after the fader level changes, meaning level changes
to the main mix will also change the level to the mix or FX send.
Normally monitor mixes at set to pre fade as you don’t want the monitor levels to
be changing as someone makes adjustments to the main mix.
FX sends/mixes are normally post fade as you do want the send level to track along
with changes to the main mix, if FX were set to PRE you could turn down the main mix
level but still hear the full FX return of the channel.
You can globally set the mix pre and post options in the mix set up menu by selecting the mix and you can also set if you want the mix send to be pre or post EQ or processing.
Pre & Post fade mixes are not just a digital mixer thing, they’ve been on analog mixers
in some form from the beginning.
