12AU7
The 12AU7 (European type ECC82) is a twin medium-μ triode tube with a center-tapped filament for use in either 6.3 V / 300 mA or 12.6 V / 150 mA heater circuits. It is likely the first tube manufactured with a B9A (Noval) miniature 9-pin base (from 1946).
The 5814 is a high-rel version with increased heater current.