i've been checking my notes about nx1 hiss. check them at https://www.head-fi.org/threads/the...utorial-in-post-2.800208/page-6#post-12994430 "In low gain, the hiss is maximum (and clearly noticeable) at minimum volume, and goes lower when raising the volume (it is low at 3/4 volume, and it disappears at maximum volume). In high gain, you get maximum hiss at minimum and maximum volume, less hiss at medium (12h) volume." after measuring it, decided to only use low gain mode. in that mode, you'll probably set high volume, and hiss is minimum there. i got the nx1a for longer battery autonomy. it's very affordable, and i think it would be suitable for zs5 and other low impedance. i dunno about its power (limits of current regards of load) and distortion. i should measure it with zs5. will do it. EDIT: nah, forget it. low current capable. higher distortion than desirable. not suitable for ZS5.