(slightly microphonic) 6SN7GTA GE NOS 1952 copper grid posts (7.4/10ma)
2.7.25 (!!!!!) (Recommended Pair) 6SN7GT Tungsol parallel gray plates large "O" mica ears NOS 1953 (6.4/6.6ma and 6.4/6.8ma) (rare version) (Cary, Rogue)
6SN7GTA CBS NOS Black Ribbed Plates similar to RCA early 1950's (8.3/8.6ma)
6SN7GTB CBS black base black plates side-getter, the same shape as Sylvania 6SN7GTB used/good 1961 (7.5/8.0ma)
6SN7GTB RCA used good 1960's (6.4/8.2ma)
