Unity Gain
 

I'm taking some ARP courses based on Pro Tools and we had a discussion regarding the master track and unity gain. Whether or not the master track should be left at zero db. When is it ok to change this if ever?

Re: Unity Gain
 

You're right about leaving the Mastertrack Fader at 0 dB.

Personnaly I use (I mean I put it down a bit), till the very last moment (just before the Bounce to Disk command).

For example when you record your tracks, you will left this first track fader set to 0dB, for the moment.Then recording the other tracks, you won't each time low down the previous track to have a decent Stereo sum level.
Once all your tracks are recorded, edited and mixed, obviously, your mix should be balanced but....your overall level (thru the Master Fader) will be, I'm pretty sure, too hot for the DAC.
This is mainly because your ears get use to high level (ear fatigue and psychoacoustic!).

At least with this lower Master Fader setting you don't have to care too much about levels during the "creative" work.
It's a kind of cushion to protect your DAC.Then you can fully focus on the "artistic".

To reach the proper level, select Group All then turn down all your fader proportionnaly, then turn up your Master Fader to 0 dB (can't remember if the Master Fader is include in the Group, if so you'll need to activate and desactivate the Group few times untill you reach an overall mix level between -10 and -4 dBFS average.)

Basically you use it to prevent dynamics clips and artifacts, just like a Monitor level controller.

Hope it helps.