Not really stock but... I designed my own HDMI I2S board but the later AGD version works and is pinned out the same/ functions identically. I do not own a Master 11 but since it is PCM only should be the same as the Master 7 as far as how its HDMI I2S port works. But you can say my Master 7 works just like the factory built models.
I can't comment on the NFB-28 and DSD over the HDMI I2S interface. That is another mode specific to sigma-delta DACs and doesn't apply to ladder DACs. But you can also send PCM over HDMI I2S to the NFB-28 and that mode may have the same connection issues as the Master 7 but don't know for sure. These would be Kingwa questions or perhaps someone familiar can clarify.
If you have no ability or find someone to modify the Gustard U12 HDMI I2S port (or cable) then it will not work correctly and/or give best performance with any of the AGD products as they all use the same HDMI I2S receiver board. The U12 only works for me with PCM to the Master 7 as it is modified to conform to the PS Audio method, The U12 though with work great as-is with a Gustard DAC over HDMI I2S as they are both pinned out to be compatible. You would though have the exact same signal polarity issues going the other way with say using the Off Ramp 5 and a stock Gustard DAC. There is a lot of confusion in this area as there is no industry standard for I2S over the HDMI hardware and seems every manf. does something differently. But the PS Audio method does work for a lot of higher end DACs and seems to be favored - at least in N. America.
I'm going to make a custom HDMi cable and I just need a little guidance on how to modify the pins.
What should be done to side A for audio-gd and side B for bustard gustard.
Assuming that only one end of the cable needs to be modified? Please advise.
I bought a couple cables that can be opened, also a breakout connector with plastic cover, and basic connectors too. Will make something they hopefully works.
I'm just trying to avoid modifying the gustard u12.
I'm "ok" with a soldering iron so should have no problem. I want to be sure I have a visual of what I need to do. I'll be sure to label the cable for custom use and only use it with the master 11. If it sucks, oh well. I will report back. And sell my u12 on here or return to Amazon. Depending on what I can do.