I am using an unrooted Galaxy Nexus, with the Stock ROM. I found that when I am playing high bitrate mp3's, and the display turns off, the music or podcast I am playing would start to pop and sound terrible.
I've searched high and low for a way to fix this problem, to no avail.
Recently playing with my GNex's sound settings, I found a solution!
1. Install Volume + Free (https://play.google.com/store/apps/d...cm9pZC5sdmgiXQ..)
(or the paid version: https://market.android.com/details?i...roid.lvh&hl=en)
2. Go to Settings > Sound > Music effects > Make sure that "Volume+" is selected.
3. Open your music player, and while playing your music or podcast go to the settings tab (those small dots in the upper right hand corner), and select "Sound Effects".
4. Go to Headset settings, and check "Virtual Room Effect"
5. Go to Virtual Room and select "+1" level.
These settings worked for me. The music or podcasts sound a little different, like they are in big room, but not too bad. The best thing is that the playback is now smoooooth.
There might be other settings you can try that may work, but I think the key is to create an environment where the CPU will not clock down when the screen is turned off, but stays active applying filter effects during playback.