I just picked up the ZTE Axon 7. I was quite shocked as it was able to drive my headphones (although near max) volume without an external amp. I tried the HD650, Audeze LCD2, and Fostex TH900 headphones. It was able to drive all to comfortable listening levels. I was especially shocked when it was able to drive the planer LCD2s. I then tried it with a Cayin C5 external amp (that has been modded) and I must say that the sound is impressive in comparison daps and tabletop systems. I did a quick comparison to the Plenue P1, Onkyo DP-X1, Oppo HA-2, and Oppo Ha-1. I must say that this phone has the best audio quality I have heard in a mobile phone. I prefer the AKM sound signature in comparison to ESS offerings such as in LG's V20. I find ESS to be shy on the lower end of frequencies and I like to have my bass. I was originally a Samsung Note person and I have tried the new S8. I went to best buy with my HD650 to try many of the new phones. The S8 was one of the most disappointing in sound although I didn't know what settings it was on, etc. The Samsungs were built like tanks and through many falls, getting dirty, etc with years of use, it still works. I hope the case is the same with ZTE.
The ZTE Axon has a very similar sound signature to Cary Audio's Dac 200ts. (it also uses AKM dacs). I was not disappointed with ZTE Axon 7 when it comes to audio quality in a mobile phone. I only wish that the battery was removable so I could replace it with an extended battery but I will just have to live with it.
One question I do have, is there a way to disable the locking screen wall paper (ZTE Locker). There doesn't seem to be any option and I have tried No lock apps. Thanks.