(!!!!!) (Best Overall Single) JAN-5691 Sylvania black plates NOS 1977 (2.8/3.1mA) (Same Gm) (Best 6SL7GT sub) (same internals as 5691 red base)
(!!!!!) (Best Value Single) JAN-5691 Philips by Sylvania black plates NOS 1985 (2.4/2.6ma) (Best 6SL7GT sub)
(!!!!!) (Recommended Single) JAN-5691 Sylvania black plates NOS 1979 (2.2/2.4mA (Best 6SL7GT sub) (same internals as 5691 red base)
(!!!!!) (RecommendedPair) JAN-5691 Philips by Sylvania black plates NOS 1984-1985 (2.0/2.2mA and 2.1/2.4mA) (Best 6SL7GT sub) (same internals as 5691 red base) 1-3% matched
5R4GYB Sylvania NOS 1970's (52/40 and 49/40)
