I also hear a very slight hiss with the emotiva mini-x and HE-500. From reading this entire thread I believe they all have a small noise floor, but that the people claiming they hear nothing either don't have as sensitive hearing or have not actively listened for it at 0 volume. It does get much louder towards 2 on the dial, but with a normal dac you shouldn't need the volume that high. That's my take on it for what it's worth.
Actually I am not interested in HE500 but HE-4 / HE-6 so with their ultra low sensitivity there sould be no sign of even small amount of hiss ...
Do you have any technical info about up to what power it stays in A class, max peak to peak voltage, distortion values at different power output ? (read somewhere about 80V p-p but don't know the source)
Edited by magicman - 10/18/13 at 12:04am