You should talk to Lynx... There's no reason why the unit shouldn't work just fine with ADAT as sync source. Word Clock won't likely solve this.

Regards
Daniel Fuchs
RME

Thanks for your answers.

I have the latest firmware already.

And yes, it is a one way connection. (At least it seems like that to me)
ADI 2 Pro (Internal Clock) -> AES -> RayDat (Ext Clock) -> ADAT -> AURORA 8 + LT-ADAT (Ext Clock)

Many times the system works just fine but the Aurora looses the 'connection' once in a while and needs to be 'brought back' by switching through sample rates. I did a firmware update for the Lynx yesterday and maybe that helped.

By the way: Lynx Support told me:
'ADAT is horrible for clock because there is so much jitter. Please try Word Clock and let us know what happens...'

Before I purchase the WC expansion for the Raydat I'll wait a bit and see if the fw update solved it.

Why not try the Lynx as master? Steadyclock in the raydat and ADI will remove any jitter. Lynx admits that its external clocking is not optimal, so you probably get a little improvement on the Lynx as a bonus.

In your setup with the ADI-2 Pro being used for phones and monitors you do not need to worry about D/A conversion quality.

The ADI-2 Pro removes any jitter from the incoming digital signal and finally uses its own built-in clock to perform the final D/A conversion towards phones and speakers.

And this has such high quality, that you really do not worry about it. I used ADI-2 Pro and now ADI-2 DAC in front of a High-end HiFi and I have to say that the RME device is even a little bit better than the Accuphase DAC-40 DAC module of an Accuphase E-600 Class A amp with B&W 803 D3 speakers.

Sorry, I can't remember whether the other direction (A/D) has been discussed already on forum in terms of clocking.

Personally I would simply guess, that its also decoupled like for D/A, but tbh, I don't know exactly.

This is something that only RME can answer to you.