apart from your specific question, I have taken the liberty of addressing a few other points further down that are related to the question of whether one should upgrade to a UFX III, in order to provide other readers with a more comprehensive overview.
Generally spoken, you can assume that RME would not use USB3 if the product did not function perfectly with it.
Here are a few examples from my experience with my UFX+ over USB3 (as I have no TB).
I have not experienced any general issues with USB3, only a few things explained below, that can easily be solved and which is nothing unusual according to the complexity of today's computers. Incompatibilities can also happen with TB.
Regarding USB3 performance. I conducted a "synthetic" Cubase benchmark with a 400-track project containing over 800 Steinberg VSTs (2 VSTs per track), and it performed excellently without any dropouts at both 44.1 and 96 kHz.
The system load was comparable to a RayDAT PCIe-based card. You can find more details about this benchmark here: https://www.tonstudio-forum.de/blog/Ent … cks-de-en/
If you should experience USB3 issues, a possible solution is to purchase a USB3 PCIe card, best with supported USB3 chipsets, which are known to work. You can find more information about this in the manual. It is generally a good strategy to isolate your recording interface behind such a card.
In my case: initially, I had no issues using the USB3 ports from the Intel C612 Chipset to connect even two UFX+ units. However, as I connected more USB devices, I encountered problems. This is when I had to isolate two UFX+ and an ADI-2 Pro behind a Sonnet PCIe card with supported FL1100 USB3 chips. You can see my system setup here: https://www.tonstudio-forum.de/blog/Ent … mponenten/. This Sonnet PCIe card uses still the FL1100 chip: https://www.sonnettech.com/product/alle … 4port.html
Since using the Sonnet USB3 card (the pro model with 4x FL1100), I have not had any issues anymore. Even with two UFX+ and ADI-2 Pro connected to it.
Graphic cards for gaming can be another reason for audio drops (not USB3 or TB related). After upgrading my system to an nVidia card with RTX2070 Super, I got occasional audio glitches independent of CPU load or DPC latencies. This was related to power saving on this nVidia card. This could be solved with the tool powermizer that disables power saving on the card.
As for the differences between Thunderbolt and USB3 in terms of RTL, you will have to decide for yourself whether these differences are relevant to you. You can find more information about this here (snapshot from an Excel):
- with higher sample rates, the converter latency values become even smaller
- that the values provided in meters or centimeters refer to the "speed of sound" at 20°C. To give you a real-life example of what these ms values would mean in terms of distance between musicians on stage
- as there is no UFX III with TB I can only show the difference between USB3 and TB based on values from UFX+
For other differences between the UFX+ and UFX III, please refer to my comparison Excel sheet here:
https://forum.rme-audio.de/viewtopic.ph … 26#p186126
These differences include very fast converters, improvements in the analog section, USB3 CC mode for all I/O ports, FS clock, track names for DURec, remappable keys (33 functions), and lockable keys. The latter two features were first introduced for the Fireface series by UCX II. Additionally, both ADAT ports on the UFX III are switchable to optical S/PDIF.
What I also like about USB3 is the maximum cable length of 3m. That's 1m longer than Thunderbolt and allows me to have the rack on the left and the computer on the right side of the desk. With a 1.5m wide table, you already need around 3m if you have to cable along the wall or along the corners. I've had good experiences with premium cables from Lindy here, which offer triple shielding and in my opinion provide good connector quality. The price-performance ratio is very good compared to the very expensive (in my opinion overpriced) TB cables.
https://www.lindy.de/3m-USB-3-2-Typ-A-a … ;ci=800504
If anyone is seeking for the latest and greatest in terms of monitoring, technical specs and features: an alternative option would be to consider purchasing an ADI-2 Pro FS R BE or ADI-2/4 Pro SE. I have discussed the integration of such a reference converter in my blog here: https://www.tonstudio-forum.de/blog/Ent … our-Setup/
Additionally, some information about the benefits and features and a model comparison (ADI-2/4 Pro SE not yet in) here:
https://www.tonstudio-forum.de/blog/Ent … ses-EN-DE/
If we ignore the question whether there are audible differences in the D/A conversion between UFX+/III and ADI-2* (you should find that out for your ears in your environment): these devices offer for sure the best technical specifications, various A/D and D/A filters, and a variety of innovative and useful functions for monitoring through speakers or headphones.
Other benefit: they also provide implicit protection against high volume levels due to level mismatches (see also forum https://forum.rme-audio.de/viewtopic.php?id=25399), if one has not already addressed this through appropriate measures.
With an ADI connected behind a digital output, in TM FX, the output level can be left at 0dB for the Main Out. The ADI remembers the last volume setting and increases the volume with a slight delay when switching between speakers and headphones, which is enough to reduce the volume.
I hope that this overview will help you in deciding whether to stay with the UFX+ or upgrade. The UFX+ remains an excellent interface and delivers the lowest RTL values, even though the differences are minor. Your setup seems to be functioning well, and technical specifications aren't everything in this world.
BR Ramses - UFX+, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1650v4, Win10Pro22H2, Cub12Pro