Your saying that because attenuation is done in the digital domain the analogue stage, after the D/A conversion, would be set at unity gain and because of this your getting noise on the outputs regardless of the volume setting. Am I right?
The thing is if this were true then the analogue stage after D/A conversion would need to be pretty bad to introduce noise. That or something is wrong.
As it stands my unit is fine and doesn't produce the hiss your mentioning through my monitors, that are set at unity gain, and subsequently I use my MR816 as the monitor controller...