My NFB-11.28 arrived two days ago. Right out of the box the sound was very good and the amp is powerful and distortionless as I expected, based in my previous experience with NFB-12 and NFB-15.1. I am using it with the DT-990Pro Beyers. I expected a warmer sound but it seems to be rather neutral. May be my expectations were due the experience with the other units based on the Wolfson chip that had a warm character. The unit is still burning in, so I cannot tell how good it sounds, yet. So far it is excellent for the price. Compared to the Yulong Sabre DA8, as a DAC connected to my main system with speakers, I consider the Yulong superior with a smoother sound, more realistic and a bit warmer. The Yulong took a very long time to reach its best sound. I believe the NFB-11.28 will improve with time, too. I did not play with filter and sound jumpers, yet. I'll let the unit run in before start playing with them.
I consider the NFB's amp much superior then the DA8's one. It is incredible how loud it can drive the Beyers without distortion. Be careful to not damage you ears. This amp can play loud, very loud and you will like it due the excellent drive and low distortion.
Both DA8 and NFB use Amanero USB input, but it seems to work better with the NFB. It played DSD512 better than the DA8, however both produce some noise at this rate. I consider both good up to DSD256, only. The optical input works up to 192 kHz with no problems, despite the specifications limit the sampling rate to 96 kHz. May be at 192 kHz the performance is not guaranteed, but it can work, depending of the source. I did not test the coaxial input, yet.
When I inspected the case, I was surprised that the ventilation holes are in the bottom cover but not on the top one. The unit gets just warm, not hot at all. I remember my previous NFB's got hotter than this one.
This is all for my first impression of this little wonder.
Update: After some more listening sessions comparing with DA8, I now think that Yulong DA8 is not warmer than the NFB-11.28. After some more hours of burn in, the sound quality improved a little. The NFB has more punch than the DA8 but the Yulong's midrange is still more informative. Despite this, I am starting to like the NFB better more than the DA8. It is not as refined but it is a little more enjoyable. Both are very good DAC's, though. May be they have different flavours.
I was able to connect he NBF-11.28 to my Moto X 2 via OTG adaptor. Tidal and Spotify sounded very good. The DA8 input did not work with any smartphone I tested. It changes to DSD mode and no sound comes out of it.