If RMEs converters are superior or on par with the ones in the other devices I am leaning towards the UCX II as it would offer more channels than the BBF Pro FS.
The BBF Pro is designed for being compact, to also support mobile applications. It's the only RME recording device which can be driven USB bus powered. But at the same time RME got it managed to give this interface still powerful enough phones outputs. An advantage is, that you can use an optional power supply, should the USB power infrastructure of your computer should be weak.
As the case is quite small you have cables at the back and left/right side, so it could be an advantage to use angled connectors, so that the cables on your desk do not consume much space.
The UCX II has a more pleasent form factor, the cables are straight in the front and in the back and on top the device offers a lot of I/O possibilities and features including a complete FX chip implementation, Autoset, Durec, ...
But watching this review got me wondering why RME would use the superior clocking system of the ADA-2 in the BBF Pro FS but not in the newer UFX and UCX line?
Sorry, no time to watch a 30min video at the moment. And I am not sure what you exactly refer to, to RME Steadyclock technology (which all RME interfaces have) or to Femto Second Clock Chip, I assume you meant the latter.
Regarding TM FX design.
It is highly optimized, your comparison with Windows is really so ... hmm .. inappropriate.
Sorry, but you should first deal with it to understand why it is the way it is and why it is so really good.
BTW .. if you know how the operating concept works, you can do things with it that others can only dream of.
In the area of ADI-2 Pro the common sense is, that FS clock delivers better measurable values (higher SNR, less jitter in combination with RME's phantastic Steadyclock technology). But these changes are not audible (lets take psychoacoustic aside), because our ears do not have that high sensivity / resolution that would be required to really recognize this.
RME was here so fair from the beginning, not to make a big marketing show out of FS clock and that customer with the older ADI-2 Pro could be relaxed to stay on their older devices without FS clock.
FS clocks at a certain point simply became available on the market to an affordable price and then it has been used for the manufacturing process. When an update is due for a certain RME product, well then they get now additionally FS clock in.
You really should watch this tech video about steadyclock
and this video about the quality of RME conversion, what quality you get at a really affordable price:
I think you should also consider a combination of
- UCX II and ADI-2 Pro FS R BE or
- UCX II and ADI-2 DAC FS
ADI-2 Pro/DAC (converter / USB DAC / Phone Preamps) offer to you even more advanced features.
This in combination with a RME recording interface with TM FX ... This is really exciting.
Just look at it, I can only make you offers from my own experience.
X10SRi-F, E5-1650v4, Win10Pro21H1, Cub11Pro, UFX+, XTC, 12Mic, ADI-2 Pro FS R BE, RayDAT