Not sure about the MAC, but my some of my Parasound power amps have input attenuators and I always use them maxed out. This will give you the lowest input impedance from the driving preamp to the power amp, and will remove any non-linear effect of the input potentiometer on the sound. That is why they sound better this way.
Changing the gain on the pre-amp is another problem. I would live with the lower gain settings if overall it sounds better.
Whether the pre-amp sounds better at higher settings depends on how they use the volume control in the design. Without knowing specifics, its hard to tell.
Changing the gain on the pre-amp is another problem. I would live with the lower gain settings if overall it sounds better.
Whether the pre-amp sounds better at higher settings depends on how they use the volume control in the design. Without knowing specifics, its hard to tell.