Have you eliminated the possibility that it may be a ground loop problem?
Connected to my tube amp, with no music playing and the volume right up beyond normal listening levels, I can hear mains noise - a nasty kind of humming buzzing hash. It disappears immediately if I disconnect the mains power supply from the laptop or if I use the headphone out, so I'm pretty sure it's caused by a ground loop issue. It could also just be the dirty source power supply, in my case to the laptop, but I think it more likely a ground loop is to blame. In my case it isn't audible at normal listening levels but it may have a subtle impact on the sound - the blackness of the background for example.
Sadly my tube amp is particularly good at picking up this effect. With my Audio GD Reference 5.2 DAC it is even worse, but that's ac powered so you'd probably expect that. With the Audio GD, if I use the XLR out to a different amp, again there's no hum - pretty much exactly as you'd expect with a ground loop. Obviously with the ME you don't have that option.
I doubt the Meridian is more susceptible than other equipment to this effect, and it's possible that it will show itself in some rigs but not others, for no immediately apparent reason.
I doubt it's a ground loop. As I've mentioned previously my other two DACs (one of which is connected to the same computer via USB) do NOT have this problem. A ground loop would likely manifest itself across gear, particularly across USB connected gear. The issue is present with the Explorer, however, when connected to all three of my amps - Lyr, Crack, and Soloist. I built my computer myself and while the PS or MB certainly can't be ruled out, no other audio gear I've ever connected to the system has been problematic. All evidence points to the Explorer being the guilty party here.
Edited by swmtnbiker - 2/16/13 at 8:03am