power tube for ref 5se

I use the Tungsol 6550 Blackplate , same as in the CD REF 7.
Up until now there is none better .Fortunately I have bought spare blackplates for both units

Hello Veerapaneni,
it seems they are sold out ,I bought mine at Ebay two years ago , they were not NOS , but measured fair enough.At tubeworld.com I just saw some black plates ( used ), very very expensive ,another option is the gary smooth plate

oeps , I mean GRAY smooth plate version of Tungsol