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Power - Triode ·Triode

50

Classic directly heated low-mu audio power triode for single-ended Class A output stages. With about 15 W plate dissipation and amplification factor near 3.8, published 450 V operation provides approximately 4.6 W output.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
4D
Socket code
UX4
Base pins
4
Nominal heater
7.5 V / 1.25 A

Description

Directly heated Type 50 audio power triode. The supplied Emission Labs sheet was read for filament data, maximum ratings, representative operating points, gm/rp/mu, output conditions, capacitances, and rectifier filter conditions as applicable.

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
4D
Socket code
UX4
Base pins
4
Nominal heater voltage
7.5 V
Nominal heater current
1.25 A
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

4D - 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
1800 Ω
Transconductance
0.0021 S
Amplification factor
3.8
Max plate voltage
450 V
Max plate dissipation
15 W
Max cathode current
55 mA

Published ratings and characteristics promoted from the approved datasheet.

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

1932 Cunningham Radio Tubes

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Grid-plate capacitance

    9 pF

    Published direct interelectrode capacitance

  • Grid-filament capacitance

    5 pF

    Published direct interelectrode capacitance

  • Plate-filament capacitance

    3 pF

    Published direct interelectrode capacitance

  • Grid-cathode capacitance

    3.2 pF

    Published direct interelectrode capacitance

  • Plate-cathode capacitance

    2.2 pF

    Published direct interelectrode capacitance

  • Load resistance

    4100 ohm

    Published operating characteristic

Data set 02

1937 Raytheon Radio Receiving Tubes

Published operating points and test conditions from this source.

SECTION 1

Triode

Capacitance

  • Input Capacitance

    4.2 pF

  • Output Capacitance

    3.4 pF

  • Grid-Plate Capacitance

    7.1 pF

Other

  • Plate Voltage

    450 V

    ClassA

  • Grid Voltage

    -84 V

    ClassA

  • Plate Current

    55 mA

    ClassA

  • Load Resistance

    4350 ohm

    ClassA

  • Power Output

    4.6 W

    ClassA

Data set 03

193X Cunningham

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristics

  • Heater/filament voltage

    7.5 V

    Published nominal

  • Heater/filament current

    1.25 A

    Published nominal

  • Transconductance

    2100 uS

    Published characteristic

  • Amplification factor

    3.8

    Published characteristic

  • Plate resistance

    1800 Ohm

    Published characteristic

Data set 04

1940 RCA

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • HeaterVoltageNominal

    7.5 V

    Nominal

  • HeaterCurrentNominal

    1.25 A

    Nominal

  • Maximum Plate Voltage

    450 V

  • Maximum Cathode Current

    55 mA

Characteristic

  • Transconductance

    2100 µS

    Typical

  • Amplification Factor

    3.8

    Typical

  • Plate Resistance

    1800 ohm

    Typical

  • UndistortedPowerOutput

    4.6 W

    450 V plate

Data set 05

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Triode

Capacitance

  • Input Capacitance

    4.2 pF

  • Output Capacitance

    3.4 pF

  • Grid-Plate Capacitance

    7.1 pF

Other

  • Plate Voltage

    450 V

    ClassA

  • Grid Voltage

    -84 V

    ClassA

  • Plate Current

    55 mA

    ClassA

  • Load Resistance

    4350 ohm

    ClassA

  • Power Output

    4.6 W

    ClassA

Data set 06

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Plate Voltage

    350 V

    ClassA

  • Power Output

    4.6 W

    ClassA

Capacitance

  • Grid To Filament Capacitance

    4.2 pF

  • Plate To Filament Capacitance

    3.4 pF

Data set 07

2026 Emission Labs

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristics

  • Filament voltage

    7.5 V

  • Filament current

    1.25 A

  • Plate resistance

    1800 ohm

    ClassA

  • Amplification factor

    3.8

    ClassA

  • Transconductance

    2100 uS

    ClassA

Other

  • Plate voltage

    400 V

    ClassA

  • Plate current

    55 mA

    ClassA

  • Grid voltage

    -70 V

    ClassA

  • Load resistance

    3670 ohm

    ClassA

  • Output power

    3.4 W

    ClassA

  • High-power Class A output power

    6.7 W

    PlateVoltage=485V;PlateCurrent=57mA;Load=5k