Have checked with the Engineer of Cayin, they stated that N6 can output DoP via coaxial but limited to 2.8M only.
I have the production unit with me, but I won't be able to connect the player to my home system until weekend, will keep you informed if I failed to achieve this, otherwise you can assume the DoP via Coaxial is working.
Thanks for finding out this info.
Its a pity that it doesn't support dsd 128. I wonder if this is a technology limitation or just hardware implementation. In any case, its still decent that they support dsd 64.