how can I get DSD signal from my Sony SCD5400 ES

Are you sure there's an HDMI DSD DAC on the way? :)

Are you sure there's an HDMI DSD DAC on the way
I once asked Audiobyte and they said that in the future there may be, the problem now is the decode license from Sony. I don't know whether it can also work with those of oppo or not. I need to confirm this info later . I may be wrong but I think I'd better wait until the DSD 512 have settled and the price has come down more.

Frankly I feel HDMI is not a great transport for audio signals. The M51 for instance often sounds better using the SPDIF than HDMI.

Is DSD available with a SPDIF connection?

db

DSD is generally NOT available on S/PDIF except for modified players.