(!!!!!) (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
(!!!!) (Best Single 1960's) 5691 RCA Red Base branded GE Black Plates NOS 1960's rebranded in 1970's (2.4/2.6ma)
(!!!) (Best Value Pair) 5691 RCA Red Base gray plates rebranded GE NOS 1960's (2.1/1.8ma and
(!!!) (Recommended Pair) 5691 RCA red base gray plates 1968-1974 (2.2/2.4ma and 2.1/2.3ma)
(!!!) (Recommended Single) 5691 RCA red base black plates NOS 1957 (2.0/2.1ma)
(!!!) (Recommended Single) 5691 RCA Red Base black plates used/good 1959 (2.3/2.0ma)
5691 RCA Red Base Black Plates used 1948 (2.2/2.4ma) (Gm=62% and 75%)
