DAC that will play 196/256 files through optical input

OP, why do you want to use optical output? What will the source component be? Cheers,
Spencer

I am using a Bluesound Vault.  The only digital out is an optical output.

Bluesound Vault to the Oppo optical in, then Oppo balanced out to a Sherbourn balanced in connection

That is a shame. You do know that the Vault only handles sample rates up to 192, right? So even if you find an answer to your original question, you'd have to upgrade from the Vault to take advantage of those higher sample rates.
Also aren't the only common 256 files upsampled DSD via PC using HQ Player, etc? What kind of files are 256 sample rate that are compatible with the Bluesound Vault. Sorry, but I am getting confused about that. Cheers,
Spencer

Yes I know the Vault only samples up to196. I'm okay with that. The problem is my Oppo only samples 196 through the USB input. Limited to 96 through the optical or coax inputs.