I can change the volume of all my content with other tools if need be.
As I read http://support.apple.com/kb/ta38403?viewlocale=en_us it repeats the advice, information about the volume can differ from the source.
Bob
I use an older Shuffle as my main gym/treadmill MP3 player. I'm noticing that I can't increase the volume to my desired level after a short period of playing. It may have something to do with the source material i.e. from my CD collection versus iTunes download but I haven't been able to verify that yet. I know the playback volume is not restricted on my settings when I check it on iTunes. Has anyone encountered this issue? Maybe I'm just getting tired and my earbuds are getting sweaty but it sure seems like it's something more than that?

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