If I follow the thread and reviews... M8 has some hiss on IEMs even on low gain, 720 has a lot, AK120/HM-901 has none... that about right?
Also how does the Classic/M8 compare to the AK120 and 901/IEM for use with iems exclusively? Other options I should consider? Likely JH13fp or Siren equivalent or possibly at ER-4PT with some form of bass boost in my future.
Yes, the M8 has (to me) some barely audible hiss with some multi driver IEMs as it is perhaps too powerful for them even on the lowest gain.
This only occurs when music is not playing, when music is playing there is no hiss (I tried with Shure 535, JH13 and JH16).
Centrance will also reduce the gain of the Hifi-M8 unit on request so there is No hiss, but slightly less power as I understand it overall.
The Hifi-M8, Hifiman 901 and AK120 are fairly close overall, but with High end IEMs (I tried various Fitears and Translucent at the time) The 901 and AK120 were ever so slightly ahead. But do note at that time I was using a beta build and had not received my final version Hifi-M8.
I use my Hifi-M8 with the Touch5G and cant comment on its use with a classic.
regards.