There is a scene in Spinal Tap where a guitarist explains that his amps go to 11, one louder than 10. The joke is that the number on the dial does not mean what he thinks it means.
Lets talk about gain structure, meaning how much level each device in the chain hands to the next one. Gain structure is arguably one of the most important things to get right in an audio system. I generally run amplifier input attenuators fully open and set my levels at the DSP output stage, and plenty of good engineers disagree with me.
Opening the attenuator does not make an amp more powerful. Maximum output is fixed by the rails and the load, and no front-panel setting changes that. What the control does is decide how much voltage the upstream device has to swing to reach full output. Turn it down and the DSP or the mixer has to work harder to get there, and the real risk is that one of them clips before the amplifier ever reaches full power.
The point is not to crank every knob open. It is to match the DSP's output range to the amplifier's input requirement on purpose, so there is adequate headroom the whole way through and no stage runs out before the others. Loudspeaker protection should be deliberate, set from known limits in a DSP or a manufacturer preset, not left to wherever someone set an input knob.
I saw the bad version at a friend's small performance venue and recording studio. The Crown amps were all set to different input levels, and to get enough level out of the system the engineer was driving the mixer into clipping, chasing output that was trapped behind too much attenuation downstream. We opened the amps up, set output gain in the dbx DriveRack, and fixed the gain staging at the console. The system had the headroom all along. It was stranded in the wrong place.
There is a price to pay for my approach. Opening the amplifier inputs makes upstream noise more audible at the loudspeaker, so an oversized amp on an efficient horn can hiss. If a loudspeaker preset or an amplifier's own spec calls for a specific gain setting, follow it.
A month later, a visiting engineer had turned some of the amps back down. I set everything again and then we locked the controls.
Good gain structure is a decision, not a knob position.