50 Ohm? Uh uh dude....not when using other pieces of gear that are specifically 75 Ohm!! You don't have to terminate but if you're using a BNC T split then you would. Here's what you do.
Get yourself some 75 Ohm BNC cables...from the AD device send word clock out directly from the unit...not from a T split...
T Split on the RME card and use the open end to go to the DA unit with a T split and the terminator on it. This way it's following the patch and everything will be truly synchronous at that point.
Opus

Hi Opus Thanks for your help.
The T split is on the RME word clock in. The Lucid 9624DA has no word clock in and locks through the optical in.
I'll get off my ass and build some cable with RG6.
So shall I go Swissonic out (no T) to next Swissonic(T) to RME WC in (no T) with 75 ohm cable?
thanks Roly

Well, if the DA has no word clock in that kind of blows. Optical by nature is pretty jittery, it will work but it's best to use word clock for optical applications.
I would do Swissonic out one from Word clock out to Swissonic 2 with BNC T to RME with a BNC T and terminate the RME BNC T...make sure to use all 75 Ohm cables and a 75 Ohm terminator. That would be the proper way to get everything synchronous.
Opus

Don OPUS has said;

"If the DA has no word clock in that kind of blows. Optical by nature is pretty jittery ...."

The best work around for this problem is to keep your optical lines as short as possible. Under 3 feet is best! ..... Fats

Thanks for your advice guys.
I bought the Lucid DA 9624 based on good reviews and positive remarks at other places like this. Taking one home to try out is not an option where I live. I'll email the folks at Lucid and ask why there's no WC in.
thanks Roly