Interesting, I had hum from my Emotiva when I connected it to the PCs onboard sound card, so that is probably due to a ground loop. Connecting the Emotiva to my Macbook Air I had no hiss at all and using an external DAC I also had no hiss with the Emotiva unit. Looks like you have a noisy AC supply over there. Filters should perhaps do the trick.
I had ground loop when my hs80m monitors were plugged into the fiio e9, as well as directly into the Titanium HD. I found the only way I could control it was by using a ground loop isolator, far from ideal.
I'm assuming my monitors will do the same plugged into the mini, Will check once some replacement tweeters arrive.
Looking at the attenuators, the reviewer mentioned with too much output there could be an odd panning of sound, this is what I experience with the sound clip I shared above, pans to the left.
Will have to pick a pair up.
Edited by fluidz - 8/23/13 at 9:30am