Hi, using loopback for audio routing between different programs is the only way of efficiently dividing processing among system cores. If you did not know this, it is because the DSP chip on the audio interface will do the synchronisation and offload this specific task from the main cpu cores. This will have a huge impact the more cores that are involved. Example, synchronising 8 daws running on 8 cores, sending audio between them, not using the DSP will eat up most cpu resources for sync'ing only. Try using jackd and do this, and see you cpu cores hit the roof before you are sync'ing 4 cores. Usage can be for heavy vst processing and final mixing. This will lead to lots of loopback devices used only for internal routing purposes.
I don't know how different the various DSP's on RME cards/interfaces are, I see they have different options in Totalmix...
For example the card I use now HDSP 5632, will only show the extra 4 in and out if these expansions boards are connected. But I do think these connections could be used for loopbacks even if not connected.
So getting to my point. Could it be possible to add some more loopback/internal routing only channels to the the RME system?
Looking at the DSP meter of the UCX it was obvious not using all available resources.
Using up lots of channels for loopback only is a waste of resources also...

Yes I am considering using the HDSPA Raydat and use 2(8x2) of it's adat connections for loopback only. Then again I get a usable mixer for 650€...
How do I connect a headphone to an adat interface, perhaps a headphone amp of some sort...