Originally Posted by kkcc
I had many issues with zx1 and hiss wasn't one of them. I don't recall any hiss on my Fitear tg334 or my JH13fp, which are both quite sensitive to hiss. I had not been able to test this in an absolutely quiet environment but find myself liking the black background. Similar with PHA2 I find it very clean also. Would you happen to be charging when you listen? I had DAP that has hiss only when charging.
I thought you may have hit a nail there, because I do listen to the ZX1 most of the time while having the USB connected to the PC.
However, I tried your suggestion, and unfortunately it did not fix the hissing issue.
I understand different people might have different hearing when it comes to tolerating the level of hiss.
So try this...
1) with the ZX1 turned on (but screen off) aka idle - wear your fones.
2) press the power button at the side to wake up the Lock screen.
3) you should hear a short burst of hiss that should be apparent enough in a quiet room.
4) the hissing does die down shortly after the initial burst, but it does persist throughout the usage of the DAP.
Although again, depending on your ears sensitivity, that level of noise floor might be negligible or unacceptable for some.