Synchronization

Hallo Volumio team.
I have a issue with raspberry pi and Volumio!
I have problems to synchronize my Libratone zipp with my raspberry pi, there is a time difference of a few ms . If I change my raspberry pi with an airport express the synchronization is fine. Is there a solution to the problem so i can play the good sound in the living room through the raspberry pi and the Libratone zipp in the bed room?
Best Regards Holm