Any digital system needs the sample clock to be supplied by one piece of equipment (called the master), with everything else synchronized to the master.
It sounds like you should probably set up the Ensemble as the clock master, and synchronize the H8000 to it. If you are connecting ADAT from the Ensemble to the H8000, all you have to do is to set the H8000 clock source to "ADAT".
Another, possibly better, option is to use the Wordclock output from the Apogee. Connect this to the H8000 WordClock in and set the H8000 clock source to "WordClock". The H8000 will then track the Apogee at all times.
