(!!!!) (Best Value Single) ECC83=12AX7 Telefunken Germany <> bottom ribbed plates branded GAP/R Computor tube used/good 1956 (Gm=1400/1500 and 0.8/0.9ma) 1-5% section balance1 low noise tube) ECC83=12AX7 Telefunken Germany <> bottom ribbed plates branded GAP R Computor tube used good 1956 (EC) very good printing in white box 1 section) 1. 1ma Gm=1700 1 section) 1. 5ma Gm=2000 Good used mA = 0. 7 0. 9mA+ Good used Gm = 1300 1500+ recommended for: Se Electronics Z5600a II Tube Condenser mic Veloce Audio Line Stage and Phono Amp Nagra PL L preamp VTL 7. 5 preamp MFA preamp Orange amps Conrad Johnson Premier 15 phono preamp