I have a Crown Microtech 2400 and it has an input selector, where you can choose between 0.775v and 1.4v input. The Crown is easy to drive into clipping on the 0.775 input with standard hi-fi preamps but the 1.4v input isn't.

Anyway, I like to have the levels set so that the preamp volume knob reaches clipping when it is at about 95% rotation, if the source level is 100%. I like to be able to push the amp just up to its clipping level, but not beyond it. Most systems allow going well past clipping, and that way if the input is very low, you have the gain to turn it up. But I have so much power and overall gain that I don't need that. I just like setting it so it can't reach clipping, but gets almost there. That gets me all the amp can muster, but no more and no one can twist the knob so far to get it there, no matter what source material is used. That's just how I like my system set.

Wayne