(!!!!!) (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 (2.4/2.5mA and 2.5/2.5mA) 1-2% matched (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 1978 (2.2/2.4mA (Best 6SL7GT sub) (same internals as 5691 red base)
(!!!!!) (Best Single) JAN-5691 Sylvania black plates NOS 1979 (2.4/2.5mA (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 Overall Single) JAN-CRC-5691 RCA Red Base NOS 1958 (2.1/2.1ma) 1% section balance
(!!) (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
5691 RCA Red Base Black Plates used 1948 (2.2/2.4ma) (Gm=62% and 75%)
