For some reason I am no longer able to adjust the bass boost on my Play Music app, it's not grayed out for some reason, wondered if anyone else had the issue an managed to sort it out.
I'm on stock 4.3, tried to force stop the app etc and can't find a way round it.
I've found that when my headphones are plugged in I can adjust the BB level. However when its plugged into my car via the audio jack the option to adjust BB is grayed out. Also when I unplug my headphones it removes the option to adjust it.