Sorry, I wish I was technical enough to answer your question.
There some pictures of the insides here
It looks so basic.
I have noticed that when I use a non Pass Labs or Threshold power amp ( e..g. Marantz SM-10, SR7012, Yamaha AS-3200, A-3080 and many others) then the 3D feeling almost...
I bought Topping D30. I tried tried it for 3 weeks.
Could not get the 3D sound.
It produces no noise, has excellent drivers, remote etc. Everything is perfect except no 3D sound.
Korg is less clean, has horrible drivers, no preamp output. But it produced that 3D sound even with the non hi res...
I have exactly the same case.
Korg DACs with CS4398 give me 3D sound. I have not heard Xonar but tried other CS4398 based DACs. They all have that distinct pleasant signature, though only Korg gives me the proper 3D sound.