Soweit ich weiß, hat der iPod eine Lautstärkelimitierung auf Grund von EU-Recht. Versuche einmal folgendes:
Connect your iPod to your PC. Make sure your hidden folders are visible.
Navigate to the "iPod_control" folder. This will be a hidden folder. Once you've found the "iPod_Control" folder, navigate to the "Device" folder.
Locate the file named "_volumelocked" in the "Device" folder. Delete this file.
Eject and restart your iPod.
Navigate to "Settings" on your iPod. Select "Volume Limit." You'll be able to reset your volume limit with a PIN or password.