Source volume level controversy

[eerkom]

Hey. I could really use some words of wisdom here. I recently purchased a Marantz PM6005 amplifier and Polk tsx220b speakers to go with it. The amp is hooked to my PCs soundcard via S/PDIF. I always assumed that when you use S/PDIF, you cannot even change the volume level from the source, since only the music is sent digitally as ones and zeros.. but to my surprise I found out that the windows volume adjustment works normally (as does the volume adjustments in media players). So my question is, on which level I am supposed to keep my source volume (windows pc, music played with itunes): I have gotten so mixed information on this. Someone mentioned on this forum that I should have the PC volume maxed out and only control the volume from the amp, yet on another forum someone said I should keep the PC volume on 50% cos this is somehow supposed to make the sound better and tmake the amp perform better. Getting really confused here.

Also, I've noticed that when im listening to music really loud, some bass frequencies start to distort. Still the volume level is something the amp and the speakers should easily handle. Could this be due the fact that ive had my PC volume at 90% and I should set it lower and increase the volume from the amp? (itunes player volume has been always on max)

Any advice would be greatly appreciated.

 

[americanaudiophile]

The volume control of your PC is digital so when you turn the volume down you are reducing the number of bits and that reduces the quality of the sound so it should be maxed out. With MP3s you might not notice this at all. With higher quality files it is more likely but not for sure.
Since the output is optical it can't overload the input of the Marantz the way an analog signal might so that can't be the cause of the distortion
The bass distortion is being caused because your speakers can't handle the bass at that volume or the amp is being clipped (being asked to product more power than it can which causes distortion that is usually in the treble).
There is certainly some music that will have enough bass content to do this to your system especially if you are boosting bass or trying to play it louder than it can cleanly play. If you are using bass boost anywhere turn it off (or at least down).