Antipodes development focus is (to my understanding), to bring the best signal to a DAC.
I learned from them, that Ethernet and USB carry too many distortions to become the digital connection to a DAC.
I2S ist best, followed by AES/EBU and SPDIF and a separate clock connection.
K50 is their best interface to connect internet and HD files to a DAC,
providing I2s and AES/EBU and SPDIF plus a separate clock connection
Using Ethernet or USB as connection to the DAC does sound significantly worse than I2s, AES/EBU or SPDIF.
(Using the Ethernet, USB and AES/EBU or SPDIF connections on Brinkmann Nyquist II)
According to their own goals, K40 cannot be more, than just a compromise .
So I decided to go for K50. Using the K50 for all rendering and decoding, sending only uncompressed files to my DAC.
I thought that with my previous DACs, finding USB and AES to be the best with one (ethernet being one of the worst in that DAC) and then AES to be the best with another prior (that didn't have ethernet). I spent several months and several device purchases to make I2S work "better than all others" and I never got there.
I didn't find the same results with the Rossini (which doesn't have I2S, btw)...the inputs are a lot closer to each other than previous DACs that I've owned (I own 6-7 now) and countless others I've heard in my system from friends, and I can't hear any downside with the ethernet connection to the Rossini when the chain is connected in the way I described specifically earlier in this thread. I am assuming the proper switch clocking, isolation, and very good cables are a requirement to feel this way, btw.
Your different findings are another data point for why I suggest the results are very DAC-specific and system-specific.
As an aside for ethernet, I place an extremely high priority on streaming music due to its instant availability and source material that I never in a million years would have guessed I would be so happily streaming in my nicest systems--stuff like YouTube and BandsinTown.com live concerts, and even lower-rez internet radio. Quboz and Tidal obviously are other significant sources of diverse and new music that many more trust quality-wise. Streaming requires the same investment in your network switching and ethernet from my experience, and the has the side benefit of bringing the ethernet-to-DAC a LOT more in line with other connection methods, and maybe even better than some in certain cases. I would have doubted it had I not convinced myself through a lot of testing (and spend, unfortunately).
One note AGAINST Ethernet...it may be the most EXPENSIVE to get right, so its VALUE proposition might certainly be challenged in many cases. However, for me it's performing at incredible levels and it's going to take a hell of a lot for me to go back to AES or USB, at least with this DAC.
I appreciate that others have different experiences with it, and I'm not arguing against contradictory experience to mine.