No hiss at all from my HM-801 to my JH16Pro. Dead quiet, except when you first ON the 801, it has a power on click sound which is moderately loud. Used to not put on my IEM until it is power on.
No hiss sound at all after that from the lowest volume to the loudest, and the background is completely silent even if you twist and turn the 3.5mm plug. This is same for all the amp modules I have (2 standard amp module, GAME module and Balanced Amp Module).
Confirmed nothing wrong with my JH16Pro, as I can hear hiss from DX100 when tested 2-3 weeks back at a normal volume, and if twist the 3.5mm plug, there will be interference sound. Maybe it is static built at the connection area due to no grounding?
Frankly speaking, after tested all the DAP and external amps (DX100, iMod4, iMod5.5, Sansa Clip, Sony X1060, T51, Korg MR2, Fostex HP-P1, Iriver H140, etc), nothing comes close to the SQ of HM-801, especially with the Balanced Amp Module. You have the highest clarity that is better than all the DAP that I have tried and yet produces music full of emotion and with analogue sounding.
This has been my companion for long flights which I can listen to it for more than 10hours straight non-stop without fatigue, with travel charger on. No other DAP comes close.