(!!!!!) (Best Overall Pair) JAN-5691 Sylvania black plates NOS 1977 (2.3/2.6mA and 2.3/2.6mA) (Best 6SL7GT sub) (same internals as 5691 red base) 1% matched
(!!!!!) (Best Value Single) 5691 RCA red base black plates NOS 1956, etched 1957 on base (1.9ma/2.0ma)
(!!!!!) (Best Pair) 5691 RCA Red Base Black Plates 1957-1963 same build (2.4/2.5ma and 2.4/2.6ma)
(!!!!!) (Best Pair) JAN-5691 Philips by Sylvania black plates NOS 1985 (2.3/2.6mA and 2.3/2.4mA) (Best 6SL7GT sub) (same internals as 5691 red base)
(!!!!!) (Best Pair) JAN-5691 Sylvania black plates NOS 1977 (2.1/2.2mA and 2.1/2.3mA) (Best 6SL7GT sub) (same internals as 5691 red base)
(!!!!!) (Best Pair) JAN-5691 Sylvania black plates NOS 1979 (2.0/2.1mA and 2.1/2.1mA) (Best 6SL7GT sub) (same internals as 5691 red base)
(!!!!!) (Best Quad) JAN-5691 Sylvania black plates NOS 1979 1-3% matched (Cary, Rogue) (Best 6SL7GT sub) (same internals as 5691 red base)
(!!!!!) (Best Single) 5691 RCA Red Base gray plates NOS rebranded Westinghouse 1966 (3.1/3.2ma) (Highest mA and Gm)
(!!!!!) (Best Single) JAN-5691 Sylvania black plates NOS 1979 (2.2/2.4mA (Best 6SL7GT sub) (same internals as 5691 red base)
(!!!!!) (Best Value Pair) JAN-5691 Philips by Sylvania black plates NOS 1984 (2.0/2.1mA and 2.1/2.1mA) (Best 6SL7GT sub) (same internals as 5691 red base) 1-2% 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) 5691 RCA Red Base gray plates low hours/tests like new 1966 - broken center guide pin (2.5/2.6ma) 1-2% section balance
(!!!) (Recommended Pair) 5691 RCA red base gray plates 1968-1974 (2.2/2.4ma and 2.1/2.3ma)
(!!!!!) (Best Pair) 5691 RCA red base rebranded GE NOS 1960's tiny nicks on each base (2.3/2.4ma and 2.4/2.4ma)
(!!!!!) (Best Pair) 5691 RCA red base black plates NOS 1956-1957 (2.2/2.3ma and 2.1/2.4ma)
5691 RCA Red Base Black Plates used 1948 (2.2/2.4ma) (Gm=62% and 75%)
(!!!) (Recommended Single) 5691 RCA red base black plates NOS 1957 (2.0/2.1ma)
(!!!!!) (Recommended Single) JAN-5691 Sylvania black plates NOS 1979 (2.2/2.4mA (Best 6SL7GT sub) (same internals as 5691 red base)
