-
Ahh, that's not gain - what your DAC is doing is producing the music more faithfully ie: reproducing the originally recorded signal. Although some DACs are known for being too analytical and cold. It's partly the reason why the vague and warm sounds of analogue are so appealing.
The sony Z3 will have all kinds of hardware and firmware based settings that affect sound. Could almost guarantee there's bass enhancement built in along with high gain.
I wouldn't worry about it though, it's an expensive rabbit hole to go down if you start listening too hard.
No gain unfortunately - but I think it might have something to do with the source, sounds pretty flat through my PC, but strangely much better through my Sony Z3 phone.