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!
Don't know about your Cayin, but everything I have had with a tube shield seemed to sound better without it. The exceptions are phono preamps where the shield helps decrease noise. Is that tube mounted horizontally? Seems like it might run a bit hotter with a shield. I have been very interested in this player. Would you care to comment on your first impressions of it's sound? Maybe you could treat us to a review after you spend some more time with it.
Radiotechnique 12AU7 1965. sweet with great clarity and soundtage
I really like the Telefunkens. They are bulletproof. I'm not a fan of shields but do have the rubber rings on my amp gain tubes. They reduce some of the noise from room acoustics.
2nd Beerad.Also the Mazda.I believe Upscale Audio has these for sale.
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-60 review: Hifiharv asked me to do a review, so I did one. It's posted in the Reviews section.
Opps!(Type O) My review for CD-50T