Ah, yes, AK240 doesn't output DSD at all via optical. Not sure if this can be fixed by a firmware update in the future.
Secondly, yes, even using optical out (the only possible connection between AK and Hugo), the SQ is different between AK240 and AK120. Not sure why but it's noticeable (I suspect not just to me but should be to others as well).
It got fixed by the last update
Dsd now outputs thru optical as 176 PCM