(!!!!!) (Best Tungsram Pair) ECC83=12AX7 Tungsram Hungary NOS 1969 (1.1/1.2ma and 1.0/1.3ma) 1-3% matched
(!!!!) (Best Pair) ECC83=12AX7 Tungsram Hungary NOS 1980 (1.0/1.1ma and 1.0/1.2ma) 1-2% matched