(!!!) (Recommended Pair) 71A Sylvania and Sylvania branded Tungsol NOS 1947-1950 same build (30.2ma and 32.4ma) (Highest mA and Gm)

1 pair) 71A Sylvania NOS made in 1947 printed in 1949 and 1950

1 tube) 30.2ma Gm=1900 printed in 1950

1 tube) 32.4ma Gm=2000 printed in 1949 branded Tungsol

Tested on Amplitrex

Vplate=180V

Vgrid=-38V

Good Ma = 20ma

Good Gm = 1600-1700

(71A=5V @ .25A Filament)

Mu=3

Rplate=1.82Kohms

Rload=3Kohms

Pout=0.4watts