Interesting but I'm not sure I understand what you mean. I always run my DACs in line out mode (0 dB). I have auto ref off. I wonder if auto ref is causing noise in your scenario.
I don't think I'm getting noise when the RME is not playing but I'll check it. May take a while...
OK, thanks. What I mean is that there is some noise whether the volume is off or on at any level with no music playing. As soon as the music is playing it covers this faint background noise. It does this in auto-ref ON or OFF mode and goes away immediately when disconnecting USB from the RME. I will recheck this tonight.
By the way, line out mode at 0 dB would mean that I have almost zero play on the amp volume. So I use -10 dB on line out. Otherwise by 10 o'clock on the tube amp I would be destroying my ears (I think, I have to check again, but at -10 dB at least I can adjust up to 11-12 o'clock depending on the track). How do you manage this high volume thing? I don't have the amp on high gain or anything, it's a WA3 and my headphones are high impedance Sennheisers.