It is indeed a shame, that in equipment of this price and quality, the USB input is not as refined as the rest of the entries and from what I read about the topic in forums and webs, seems to be quite common.
Addicted to music.
Thanks for the suggestion, although I do not know the market for this type of amplifier, in principle the technical characteristics of the LME49990 are very good. I would only dare to make modifications to the power supply. My knowledge about electronics, is not very wide.
Thank´s for reply too. I am using a device similar to the Regen of Uptone And I notice a slight smoothing of the sound. Not much but appreciable.
I´m sorry, I was not able to run the HDMI connection between the Pc and the M-51 and it's a shame, because I have the impression that it should be a good choice. Anyway, I will try to do it again, if I get it I will comment. I am using the AES/EBU connection with a DH Labs d-110 cable. Also a Wireworld Starlight 7 and the Singxer factory USB cable.
I decided to buy it, reading a post about it new integrated XMOS in the forum Head-Fi. I suppose you will already know it. I read very good opinions on the Singxer F-1 in it and I decided to replace the Yellowtec, also very good but at similar prices, by number of conections and audio quality, I prefer the SU-1. In it, the author makes a ranking between the different models, that he has tested and agreeing with him on the performance between the U12 and the Yellowtec I already had, I decided to buy the SU-1 and I am very satisfied with it .
Tomorrow I will try to show you some pictures.
The natural successor of the U12 with the U8 core, is the new generation also of XMOS with the xCORE-200. Apart from Singxer, there are a couple more manufacturers that contain it.
The Singxer F-1, is a simple and cheaper version of the SU-1 in case you are encouraged to try. Although it has no box and only a coaxial output. In the link I put on Head-Fi, there is a lot of information about it.
Sorry for my bad English. I hope you understand me. A greeting.