Picked up an HTC One last week and have been putting it through its paces. Unbelievable as a phone and makes my iPhone 5 feel cheap - well, relatively speaking.
Like my other two Android devices (Nexus 7 and Nexus S 4G), there is some EMI noise when accessing the network. It's pretty noticeable with my Shure SE420 IEMs, but it's quite a bit less than what's presented by my Nexus devices - very tolerable, but I am spoiled by my desktop rig's pitch-black background.
However, with my Grados, listening over the network to MP3/320 tracks from Google Play or lossless FLAC from my local DLNA server, I don't really notice the noise - even at the beginning when the app is loading the next track.
With Google Play, the volume is pretty high - at full volume it's uncomfortable for me and probably distorted, somewhat (I was test listening with Skrillex, so maybe it's the music and/or it's recording level - no offense to Dubstep fans).
With BubbleUPnP with DLNA from a local server, listening to Steve Wilson's Grace for Drowning from HD Tracks (48/24) sounds great, but I am at full volume to reach a desired listening level. Switching to the Senn HD-598, as expected, the volume lowers somewhat and I would need an external amp for active listening (background would be fine, though).
Overall, the sound is really nice, for a phone or otherwise. But switching back to my desktop rig, with the same tracks, I perceive the phone to be bright and edgy, with exaggerated bass and washed-out mids. Thinking that this could be the effect of the Beats EQ, I disabled Beats and re-played the same Wilson tracks. There is less bass when you turn off Beats EQ, but without being able to match the volume of my desktop rig, it's hard to make a fair comparison, but my opinion would be to disable the Beats EQ if you are using phones and high quality source material.
Regardless, the HTC One is an incredible phone and is my new portable, daily-driver. Now I need to find new IEMs to replace the Shure SE420s
