How many Yggdrasil impression threads are there?
Anyway, I'm going to chime in on AES/EBU, and other interfaces fiasco. I tried Allo and Pi2AES streamers, and I got to say, I'm underwhelmed. I found Pi2AES to be the worst of them all even though AES/EBU connection that is touted to be superior here. It's really not. Allo was pretty similar to USB, but I find USB best them all. I have Gen5 usb currently. Pi2AES sounds rolled-off, more blended compared to the other two. It just goes to show that just because something has AES/EBU connection doesn't mean squat. I tried the Bartok AES/EBU, and didn't sound like Pi2AES, and didn't find it to sound as and improvement over USB either. Both AES/EBU? So what gives?
So, I found Allo better than Pi2AES, and just because Pi2AES has AES/EBU doesn't really matter. I found USB to be better over both.
Something that I noticed with the both the Pi Streamers is that the sound stage seems slightly smaller imaging wise.
Lesson I learned is that, just because somebody posted Pi2AES with AES/EBU connection is superior doesn't mean it really does apply. Blanket statements doesn't apply. There's variables.
So, I will say if you use USB, no need to get into streamers unless for some functional reasons. The interfaces aren't going to radically improve the sound. Just save your money toward something else.
Big positive that I should mention with Pi streamers is that, it's cost effective streamer solution. The audiophile streamers out in the market are quite pricy, so the Pi streamers are a good solution for those looking for cost effective streamers (relatively speaking). You can use Roon with these streamers as there is a Pi OS called Ropieee out there that makes the Pi streamers compatible as a Roon node.
https://ropieee.org/
That is strange : I run the Ultrarendu through the Yggy Analog 2 with USB 5, and it cannot hold a candle to my Metrum Ambre, when running through the same Yggy Analog 2 via the AES port... Sometimes, thanks to the Schiit Eitr, I can also run the Ultrarendu through the S/PDIF coaxial port of the Yggy B, and in many respects, I prefer the Schiit Eitr S/PDIF coaxial route to the straight USB 5 route, in spite of the fact that I use a boutique made Phasure Lush USB cable with the Ultrarendu and Yggy A2...
Still, with this same YggyA2, the Metrum Ambre connected via AES , which runs on Rasberry Pi3b with piCorePlayer, but also comes armed with a humongous power supply, runs circles around the Ultra-rendu/Yggy2USB-5 or Ultrarendu/Schiit Eitre/Ultrarendu/YggyS/PDIF coaxial chains.
One more thing that some might consider somewhat "sacrilegious" : the Ambre-to Yggy B via AES playing Roon music (Qobuz, Tidal, and local files), is noticeably better performing to my ears than my Emotiva ERC-3 CD player, when hooked up to the YGGY B via AES, although, as disk spinners go, the ERC-3 is no slouch at all. So the AES itself can sound and perform differently, depending on the source that is connected to it.
What this means is that you need to take the make and quality of your renderer or streamer too into account, not to mention accessories, such as power supplies, maybe even (cough, cough) cables, and the requirements of synergy, when making such assessments, and not blame or praise too hastily, AES or USB-5 or S/PDIF on the Yggy A2 alone for the results you get.
Full disclosure : I have also tried the same Ultrarendu with the Yggy using the AES port, thanks to my Stello U3 bridge, and I preferred that AES result to the USB-5 and Schiit Eitr/SPDIF results. I can safely say, then, that in my own tests, either with the Ultrarendu or with the Metrum Ambre, the AES connection comes out ahead of the rest, but I see that as the combined result of the different synergies produced by the different streamers with the YGGY A2, along with their power supplies, and probably even with cables used, and not necessarily as a reason to isolate the USB -5 or AES or S/PDIF coaxial exclusively for blame or praise.
YMMV, of course.
It goes without saying that I am not taking issue with the SQ results you personally heard in your tests, just the conclusions about the Yggy's USB-5 and AES ports that you are drawing from those results.