Grid resistor must not exceed 0.5 MΩ with cathode bias or 0.1 MΩ with fixed bias.
Filament is thoriated tungsten and may be operated on AC or DC.
Originally designed for RF transmitter service; also widely used in audio SE amplifiers. The 801A is an uprated version of the earlier 801/10/10Y with improved plate dissipation (20W vs 12-16W).
Shares the same UX4 pinout as the 45, 2A3, and 300B directly-heated triodes.
Mounting position: vertical with base down, or horizontal with plane of plate vertical (on edge).
Pin Layout — UX4
1Filament +
2Plate
3Grid
4Filament -
Socket-Compatible Tubes ⚠ Not electrically compatible