DSD256, with “narrow” setting:
DSD256, with “wide” setting:
I cannot really see any notable differences in the DAC wideband output between the two settings. And not what I would expect comparing to the values stated in the datasheet.
Depending if the 4499EX is running at 5.6/6.1M rate or 11.2/12.3M rate, there may be only one value for DSD512. But it should work for DSD256.
Now it is not documented anywhere which of the two fixed rate families they use. But I suspect 5.6/6.1M.
P.S. It would be nice if they would offer also menu option to select the modulator as well, 4191 has configuration option to choose from (IIRC) four modulators when used with PCM inputs.