I did try the switch on the back, but it didn't make any difference.
I'm not sure if the noise on my Dacmagic plus has changed during one week listening or are my ears just got used to it, but after a week the noise doesn't sound so loud than it was before.
I think that there are no such situation where there wouldn't be any noise that wouldn't hide the noise of my DM+. I hear it only when I try to hear it, when there's a total silence on the room. On the other hand of course I want to have a unit that works properly.