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300A

Western Electric directly heated low-mu power triode designed for Class A audio-frequency output service. Low plate resistance and substantial plate dissipation make it suitable for transformer-coupled, high-quality audio power stages.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: -
Socket code: UX4
Base pins: 4
Nominal heater: 5 V / 1.2 A

Description

Moderate-power filamentary triode for Class A audio-frequency power amplification.

Socket description

Medium-shell UX 4-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: UX4
Base pins: 4
Nominal heater voltage: 5 V
Nominal heater current: 1.2 A
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 700 Ω
Transconductance: 0.0055 S
Amplification factor: 3.85
Max plate voltage: 450 V
Max plate dissipation: 40 W
Max cathode current: 100 mA

Promoted fields audited from printed ratings/characteristics; remaining published values preserved as parameters.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

2026 Western Electric 300s

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Filament voltage
5 volt
Filament voltage 5.0 volts, a.c. or d.c.
Nominal fi l a m e n t current
1.2 amperes
Nominal fi l a m e n t current 1.2 amperes
Plate current
60 milliamperes
Plate current 60 milliamperes
A m p l i fi c a t i o n factor
3.85
A m p l i fi c a t i o n factor 3.85
Plate resistance
700 ohms
Plate resistance 700 ohms
Grid to plate transconductance
5500 micromhos
Grid to plate transconductance 5500 micromhos
operating plate current are shown in Figures
7 volt
operating plate current are shown in Figures 7, 8 and 9, for a plate voltage of 350 volts.
Pm, and harmonic levels, F
2
Pm, and harmonic levels, F2m and Fsm, for each point in both the curves and the table, is numer

Other

Maximum plate voltage
450 volt
Maximum plate voltage 450 volts
Maximum plate dissipation
40 watts
Maximum plate dissipation 40 watts
Maximum plate current of average tube for fixed grid bias
70 milliamperes
Maximum plate current of average tube for fixed grid bias 70 milliamperes
limited to a maximum value of
70 milliamperes
limited to a maximum value of 70 milliamperes, so that tubes having plate currents higher than