
@Midnight > The rec output level is not affected by the master and thus it is IMPORTANT that you keep your channel levels at a reasonable level. I recommend you aim for 0dB peaks on the channels and that way your output will be roughly -19dB (the overhead of the mixer).
If you are using a 900NXS, why aren't you simply running the USB and recording from the mixer's audio interface? That way you will avoid any unnecessary noise and extra digital>analog and analog>digital conversions.