Thanks for the tube suggestions. Lots of different opinions on the use of tube shields when I searched the web. I would assume Cayin elected to use one for this player due to it's sideways mounting and close location to a circuit board.
Cayin CD-50T: Your favorite 12AU7 tube
Just purchased a Cayin CD-50T from a fellow Audiogoner. So far I've tried a RCA 12AU7 clear-top, Mullard 12AU7 long plate, and a RCA 5814 command series black plate. I like the clear-top for it's brighter presentation, as I'm using it with a Cayin HA-1A tube headphone amp. Any additional tube suggestions? Also, I use the metal shield provided with the Cayin for the tube to secure it to the socket. Anyone know if that causes overheating of the tube? Thanks!