300B

Power Triode — DHT — UX4

Western Electric

Known Equivalents & Substitutes

WE300B4300A4300BAV300BCV2609HF-300BPX300B

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Plate Voltage (max)400V

Anode Dissipation (max)Plate Dissipation (max)36W

Cathode Current (max)Plate Current (max)100mA

Max Grid ResistorGrid Circuit Resistance (max, self bias)0.25MΩ

Max Grid ResistorGrid Circuit Resistance (max, fixed bias)0.05MΩ

Typical Operating

Anode Voltage (typical)Plate Voltage300V

Grid 1 Bias VoltageGrid Voltage-61V

Anode CurrentPlate Current (zero signal)60mA

Anode ResistancePlate Resistance740Ω

TransconductanceTransconductance

Output

Output PowerOutput Power (Class A₁, single-ended)6W

Load ImpedanceLoad Resistance3,000Ω

Capacitances

Grid-to-Plate CapacitanceGrid-to-Plate Capacitance15pF

Input CapacitanceInput Capacitance8.5pF

Output CapacitanceOutput Capacitance4.1pF

Heater

Heater VoltageFilament Voltage5V

Heater CurrentFilament Current1.2A

Notes

Rg_max is unusually restrictive: 50kΩ (fixed bias) or 250kΩ (self-bias) — much lower than most power triodes; driver stage design must account for this.
DHT tube: the filament serves as the cathode; there is no heater-cathode isolation.
Pins 1 and 2 are both connected to the plate in the original WE base design, providing two physical contact points for the single anode electrode.

Pin Layout — UX4

1Filament (f-)

2Plate (Anode)

3Grid

4Filament (f+)

Socket-Compatible Tubes ⚠ Not electrically compatible

References