A possible workaround is you could process the DTS-MA audio into lossless Flac, the amplifier should then receive a LPCM stream from the A210.
There are a couple of different ways of doing it, there are a few programs with GUI's that can do it easily (XviD4PSP) or you can do it via command line (FFmpeg).
The one with the most control over the Flac parameters and an easy enough GUI is Staxrip
* Input the video stream into
Staxrip (preferably MKV ripped with MakeMKV).
* Set video encoding profile to just mux this makes it not convert video and simply copy video stream.
* Create a Flac audio encoding profile
codec = Flac
encoder = automatic
channels = 1 (Mono) - ignore the text label this converts the audio channels as is, so True HD 7.1 comes out as Flac 7.1
Sample rate = original
Under advanced de-select the downconvert to 16-bit
Now select your Flac profile and it will take the Bllu-ray/MKV file and copy the video stream into another MKV file while converting the audio into Flac. Staxrip will also preserve any subtitles and chapter data from the original MKV file in the new one.