Thanks for the input. I have the Z5 also. It's pitch black with the x7. I think it's a shame that $700-$1200 DAPs cannot remove that last 1-5% hissing in the most sensitive IEMs. I think the AK100II and AK120II are very silent.
Hi gordec, i found the hissing noise for iem is unacceptable at this price range too. But then i directly contacted Acoustic Rerearch technical support back in UK and they responded with very long technical explanation but i just want to summarize that they told me they did it because of their own purpose, they said that removing hissing noise is an easy job to do, you just simply put more filters onto the amp output to eliminate it but they chose not to do it because they want to keep the realistic and organic sound, and stimulate exactly what the song was recorded. That is why when you pair it with sensitive iems, the hissing sound is noticeable and you can just plug it with the impedance adapter and problem is solved. It's sound is more like a WOW than those AK100II or AK120II as i owned AK120II for quite sometime and i decided to trade it for AR-M2.