I don't know if mine is broken but my S9 cannot drive Aeon RT closed, it has horrible bass clicking at high volume, distortion is through the roof. On 250ohm dt770 I dont get this problem. Maybe it is the headphones.
Mine also has intereference sounds when I plug it in. It is like you leave your phone next to a speaker, sometimes when you get an incoming call there is this buzzing sound. But I am not getting any call.
But I only tried unbalanced. Will order balanced cables to try.
Also on Windows it will not let you get to the distortion level, it will be fine but Aeon will not be loud enough for some songs.
Using apple USB adapter it will also not let you get to distortion level, it will just say "this accesory is beind disabled because it uses too much power"
But if you are on android or use the hidizs lightning cable it will get louder but distort in bass, at least on my Aeon. But my other headphones are okay.
But then again high sensibility 32ohm headphones dont need this power, I can just use apple dongle.
Not really enough power for DT990 600ohm.