I am just wondering its appropriate to set the volume on iTunes to maximum and let the ADI-2 input level goes up to the red lights? That there will be no harm to ADI-2 at all and no distortion, etc.

If I set the itunes volume to any less than 100%, lets say about 70 to 80% the input level lights on ADI-2 only goes up to orange but that would be a degradation of sound if I minimise the volume in iTunes even a little.

I am using ADI-2 as D/A converter from my Mac going to my SPL Phonitor headphone amplifier I have a new model and I can set the jumper to control the output volume as well.

I have a setup like Mac > optical > ADI-2 > balanced cable > SPL Phonitor

Thanks a lot for any help.