Here is Crowns 1 pager on gain staging:
1. Turn down the power amplifier level controls all the way.
2. Set the mixer master faders and group faders to design
center. The Marantz user guide should tell you where this is for them. If not contact Marantz. They won't have faders. They have volume knobs.
3. Play a program through your mixer. On the loudest part of
the program, set the mixer channel faders so the mixer meters
peak at 0 maximum.
4. As the program is playing, gradually turn up the amplifier
level controls to the desired volume.
You may have to run the amp at full level if you want really
high volume (and your speakers can take it), but at least the
mixer will be working at its optimum output level.
Note: If you are a contractor setting up a system for a client,
you need to consider what the system user will do. Once you
leave the system in their hands, they might crank the amps up
full to get more level out of their system. When they do this,
the system might have audible background hiss, and might
clip or burn out speakers. This is an argument for setting the
gain structure with the amps open wide. You live with a little
hiss in order not to have more gain available to the user.
You could insert a compressor/limiter following the mixer to
prevent clipping, but the system still will be noisy.
Ideally you set the gain structure as suggested, then make the
level controls inaccessible. If possible, lock the amp’s level
controls in place or cover the amp with a locked cover that
allows airflow. The level controls on some Crown amplifiers
can be locked.
So, don’t worry if you have to set the power-amp knobs less
than wide open. You’re still getting all the power you need, and
the system will have adequate headroom and low noise.