(!!!!!) (Best Siemens Pair 1968) CV492=ECC83=12AX7 Siemens Halske Germany NOS 1968 1% matched (1.1/1.1ma and 1.1/1.1ma) (best in phono stages and high end preamps)
(!!!!!) (Best Siemens Pair 1968) CV492=ECC83=12AX7 Siemens Halske Germany NOS 1968 1-2% matched (1.1/1.1ma and 1.1/1.2ma) (best in phono stages and high end preamps)
(!!!!!) (Best Siemens Pair 1972) E83CC=12AX7 Siemens Halske Germany NOS triple mica 1972 printed in 1976 (1.0/1.3ma and 1.1/1.3ma) (best in phono stages and high end preamps)
(!!!!!) (Best Mullard Pair) 12AX7=ECC83 Mullard UK ribbed plates NOS 1970-1974 (1.2/1.3ma and 1.2/1.1ma) (same Gm)
(!!!!) (Best Overall Single) CV4004=12AX7 Mullard box plates NOS 1971-1972 (Gm=1600/1700) (1.3/1.5ma)
(!!!!) (Recommended Single) CV4004=12AX7 Mullard box plates NOS 1971-1972 (Gm=1500/1500) (1.0/1.1ma)
(!!!!) (Recommended Pair) 12AX7=ECC83 Philips and Pope Holland NOS 1965-1967 (2.1/1.8ma and 1.6/2.1ma) (Highest mA and Gm)
(!!!!) (Recommended Single 1955) 12AX7 BRIMAR England like new gray ribbed plates "D" getter 1955 (1.1/0.9ma) (Gm=1700/1500)
(!!!!) (Recommended Single 1959) 12AX7 BRIMAR BVA England like new gray ribbed plates large "O" getter 1959 (1.1/1.0ma) (Gm=1500/1600)
(!!!) 12AX7 BRIMAR England BVA ribbed plates used/good 1960's (0.9/1.1ma and Gm=1350/1500)
(!!!!) (Recommended Single 1957) 12AX7 BRIMAR England NOS gray ribbed plates "O" getter 1957 (1.3/1.2ma) (Gm=1700/1900)
(!!!!) (Good Value 1962) M8137=12AX7S Philips SQ France ribbed plates NOS 1962 (0.8/0.9ma and Gm=1350/1350) (Special Quality 12AX7)
(!!!!) (Good Value 1962) M8137=12AX7S Philips SQ France ribbed plates NOS 1962 (1.1/1.1ma and Gm=1550/1450) (Special Quality 12AX7)
(!!!!!) (Best Holland Pair 1967-1968) 12AX7=ECC83 Philips and Philips Miniwatt Holland ribbed plates "O" getter halo NOS 1967-1968 (1.3/1.5ma and 1.4/1.6ma) (close Gm)
(!!!!!) (Good Value Single) 12AX7 BRIMAR BVA England narrow ribbed plates like new 1959 (1.0/1.2ma)
(!!!) 12AX7 BRIMAR England BVA ribbed plates used/good 1960's (0.8/1.0ma and Gm=1400/1500)
ECC83=12AX7 Mullard UK BVA long plates "O" getter like new 1958 (f91 series) (1.2/1.2ma)
(!!!) (Best Value Single) 12AX7 Triotron by Philips Canada NOS 1963 (1.3/1.5ma and Gm=1800/1900)(same sound as Holland)
(!!!) (Best Value Pair) 12AX7A=ECC83 Raytheon by HITACHI JAPAN NOS 1960's (1.5/1.4ma and 1.6/1.4ma) (High mA and Gm) 1-3 % matched
(!!!!) (Read Review) 12AX7A=ECC83 Matsushita Japan NOS rebranded Raytheon NOS 1970 era (Gm=1800/1800 and 1.5/1.3ma) (similar to Mullard)
