In mute, without RCA or USB connected, indeed with my AKG N40 IEM and my Sony MDR-1AM2 the noise from the 4.4 balanced output is annoying, especially when you choose the bluetooth receiver. It looks like an internal electronic circuit issue.
I hope that with a firmware it will be solved, but in iFi Audio they must be very concerned.
Yeah, they responded a few posts back that it appears to be something with the baked-in software infra, and that they think a firmware update will fix it.
Once they do that, I think many of the noise complaints I am seeing (both here on Forums as well as on published written reviews online) will be amended, and make it an easy recommendation to buy