the best tube setup in a well modded mhdt orchid output buffer stage i have found is an amperex dutch ecc88 a-frame tube (o ring getter bugle boys are very close equivalents) using a garage 1217 6dj8 to 5670 pin adapter -- lovely spatial cues and subtle rendition of detail
for even greater detail old stock german siemens, philips, or hungarian tungsram tube can be used in that position - that is the fun of the tube output dacs... roll your own sonic flavor!!!