(!!!!!) (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)

1 low noise pair) JAN-5691 Sylvania black plates NOS 1977 1-3% matched 1 tube) 2.1/2.2mA and Gm=1500/1600 1 tube) 2.1/2.3mA and Gm=1500/1600   - very good detail  - low noise - reference tube   Good mA range 2.0mA+ Good Gm range 1500+    Recommended for - Ampeg Heritage B-15 - Alessandro Itallian Greyhound jazz amp- Alessandro Black and Tan 2005- Almarro A318B- Eddie Current