I'm not sure the DX90 supports DXD.. it's not listed as a feature on the iBasso website. http://ibasso.com/en/products/show.asp?ID=83
Maybe you should write to iBasso support.
I thought DX90 can downscale it to 176.4 kHz / 24 bit PCM for playback internally? Technically, the ES9018K2M DACs inside should be able to do up to 384 kHz / 32-bit DXD / PCM format.
Edited by Bluebear - 5/14/14 at 12:08pm