Phantoms accept up to 24/96 but only in Direct Optical Mode, which bypasses DOS and requires an optical connection direct to the speaker (no streaming, no app, no remote volume control etc.). All inputs under DOS downsample anything above 24/48 to 24/48, see here for a fairly lengthy discussion on the topic which arose when Devialet introduced a bug (now fixed) which stopped Roon reporting the downsampling fooling some people into thinking the restriction had been removed. IIRC this restriction was introduced in DOS 2 to improve stability in stereo pairs over wireless.