Audio quality testing by GSMarena puts it in there with all the top flagship phones http://www.gsmarena.com/htc_10-review-1434p6.php. The best phones have finally made it where maybe you might need a headphone for harder to drive phones, but DACs are really going to help much. Bought time the technology progressed, isn't it?Connecting an Oppo HA-2 to a HTC One via USB was a nice improvement in both power and sound quality. I was pretty surprised to find I prefer the sonics of the HTC 10 alone to that setup. The 10 has better sound than the HA-2 imho. Combined with the HA-2 there is more power, a bigger stage, and top end air but the 10 on its own still has the edge in my book. Headphones are B&W P7's with boomsound processing set to off.