Why does my A33 speaker quit playing even though the Bluetooth device is still playing? 

Try the following:

 

 
• Try AC operation with the AC adapter connected.  If this operates successfully, fully recharge the battery and try on battery power.
 
• Set the volume control on your Bluetooth source device at half way or above and control the volume of the A33 from the top volume buttons.  At very low volume levels on the source device, the unit may shut down after approximately 15 minutes.
 
• Reset the unit after "forgetting" the A33 on the source Bluetooth device.  A reset operation is outlined here.