Hello ,
i'm using an external A/D converter  (lavry blue)  wich send AES to my ADI 4 wich  send  adat to my rme fireface 800.
I tried to use lavry like master . I tried to use fireface like master.  i tried to use word clock cable . 
But whathever i do , when i record a hand clap, split the signal an send it one to the fireface preamp and the other into the lavry, i saw a little time delay on the time line .

Is this normal ? What can i do ?