[Re-edited here and there, pls read again]
The converters that are offered today all operate at a very high level. From individual selected technical data such as SNR or THD, something like "listening quality" cannot be derived directly.
I see here certain similarities to "ADI-2 Pro vs ADI-2 Pro FS vs ADI-2 Pro FS R BE" (the latter with even newer AKM chip).
Different technical data and feature set .. but from audible sound aspects, IMHO absolutely the same quality.
I had them all to simply be up-to-date, but to be very honest, I can't recognize any audible differences / jumps. Same good quality like I am used to in front of my studio monitors and my high-end HiFi.
Decisive for the overall quality of a product is also the correct control of circuits, especially circuit design and PCB layout, as well as RME specific features like Steadyclock to eliminate jitter. Especially in these very important areas RME has the necessary know-how and delivers the needed quality.
With RME there is no unnecessary voodoo about "mojo in the sound", RME devices are characterized by a transparent sound, which in my opinion comes closest to an unadulterated listening experience.
A much higher influence on the sound image has de facto speaker selection, acoustic optimization of the room, placement of the speakers / seating position, selection of power amp and your hearing capabilities and whether you have trained ears.
If you want to hear differences between different converters, I recommend to download the original .wav files to the following Youtube video, which was created in a professional mastering studio and get your own impression of converter differences. Here the ADI-2 Pro (old model from 2016 for ~€1650) is compared with devices Lavry and Crane Song, which are in the price range between €4000-8000. https://www.youtube.com/watch?v=doHG32aXBDY
I wouldn't focus too much on converter differences and certain technical data, from which no sound quality can be derived directly anyway (differences between 115 and 118dB, for example, no one can hear with the best will in the world).
Rather than that I would propose to better take a look at the feature set.
So when comparing e.g. the from you mentioned BBF Pro FS and UCX II:
The first thing that stands out about the UCX II are the great preamps of the UFX II, which are a real plus with 75dB amplification factor and also support higher input levels (even without PAD). With these it is much easier to get a higher level out of even quiet dynamic microphones and the whole thing as noise-free as possible. These are the same preamps that are used in the top model 12Mic.
Or e.g. low impedance headphone outputs with a higher output level, in order to be able to operate high-impedance headphones better.
And then the really great feature DURec, which wa in the past reserved for the premium models.
There might be more highlights, but sorry, I typed already a lot.. All the features and enhancements of the UCX II I put together here: https://forum.rme-audio.de/viewtopic.ph … 27#p171327
If you really want to have the best D/A conversion quality, technical data, RME spezific accumulation of genious DAC features, then you need to combine
- a RME recording interface with TM FX and the typical mix of routing capabilities, mic preamps, analog and digital ports and
- ADI-2 DAC or ADI-2 Pro like described in this blog article:
https://www.tonstudio-forum.de/blog/ind … our-Setup/
I personally think that neither BBF Pro FS nor UCX II would disappoint you, but it depends on your requirements.
If price is no hindering point, then the UCX II offers you with no doubt the better package / features.
IMHO the UCX II is a real "no-brainer" .. get it and you will be very satisfied.
As these are all aspects based on my own personal experience, may I suggest that you get both and simply try it out yourself, if you should be unsure what to buy ?
UFX+, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1650v4, Win10Pro21H2, Cub12Pro