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Power - Pentode (NOT beam) ·Pentode

EL37

25 W output pentode for high-power push-pull audio amplifiers and large power-triode driver stages.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
Octal
Socket code
IO
Base pins
8
Nominal heater
6.3 V / 1.4 A

Description

25-watt output pentode for high-power push-pull audio amplifiers and as a driver for large power-triode output stages.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
Octal
Socket code
IO
Base pins
8
Nominal heater voltage
6.3 V
Nominal heater current
1.4 A
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

Octal - 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

Pentode

X-ray radiationInterelectrode capacitances
Plate resistance
135000 Ω
Transconductance
0.0065 S
Amplification factor
10
Max plate voltage
400 V
Max screen voltage
400 V
Max plate dissipation
25 W
Max screen dissipation
6 W
Max cathode current
200 mA

Published source values promoted where applicable; additional values retained 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

1951 Mullard Valve and Service Manual

Published operating points and test conditions from this source.

SECTION 1

Pentode

Application

  • Service

    Audio power output

  • Triode-connected push-pull operation

    Published

    TriodeConnection;PushPull

Data set 02

1963 Mullard

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Anode current

    100 mA

    Pentode; Va=250V

  • Screen current

    13.5 mA

    Pentode; Va=250V

  • Output power

    10.5 W

    SingleValve; 10% distortion

  • Push-pull output power

    69 W

    PushPull; TwoTubes; FixedBias

Characteristic

  • Triode plate resistance

    1400 ohm

    TriodeConnection

  • Triode transconductance

    6500 uS

    TriodeConnection

Data set 03

1967 Mullard Receiving Tubes for Maintenance

Published operating points and test conditions from this source.

SECTION 1

Pentode

Other

  • Plate voltage

    250 V

    ClassA PentodeConnection

  • Screen-grid voltage

    250 V

    ClassA PentodeConnection

  • Control-grid voltage

    -13.5 V

    ClassA PentodeConnection

  • Plate current

    100 mA

    ClassA PentodeConnection

  • Screen-grid current

    13.5 mA

    ClassA PentodeConnection

  • Transconductance

    11 mA/V

    ClassA PentodeConnection

  • Plate resistance

    13.5 kOhm

    ClassA PentodeConnection

  • Load resistance

    2.5 kOhm

    ClassA PentodeConnection

  • Power output

    10.5 W

    ClassA PentodeConnection

  • Power output

    35 W

    PushPull SelfBias TwoTubes 325V

  • Power output

    69 W

    PushPull FixedBias TwoTubes 400V

  • Plate voltage

    300 V

    TriodeConnection

  • Transconductance

    6.5 mA/V

    TriodeConnection

  • Amplification factor

    9

    TriodeConnection

  • Plate resistance

    1.4 kOhm

    TriodeConnection

  • Maximum plate voltage

    400 V

    PentodeConnection

  • Maximum plate dissipation

    25 W

    PentodeConnection

  • Maximum screen-grid voltage

    400 V

    PentodeConnection

  • Maximum screen-grid dissipation

    6 W

    PentodeConnection

  • Maximum cathode current

    200 mA

Capacitance

  • Input capacitance

    17.5 pF

  • Output capacitance

    9 pF

  • Anode-grid capacitance

    1 pF