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Power - Triode ·Triode-Triode

25B5

Dual-triode dynamic-coupled power-output tube for high-quality audio in AC/DC receivers, combining driver and output functions in one envelope.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
2
Base
6DA
Socket code
UX6
Base pins
6
Nominal heater
25 V / 300 mA

Description

A 25 V Triadyne power-output tube developed to provide substantially more audio power than conventional AC-DC receiver output tubes. It supports single-ended Class A and push-pull operation.

Socket description

Small 6-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
6DA
Socket code
UX6
Base pins
6
Nominal heater voltage
25 V
Nominal heater current
300 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

6DA - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

2 physical sections, each with unique specifications.

Section 1

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
11400 Ω
Transconductance
0.0022 S
Amplification factor
25
Max plate voltage
180 V

Input triode of dynamically coupled amplifier.

Section 2

Triode

X-ray radiationInterelectrode capacitances
Transconductance
0.0023 S
Amplification factor
35

Output triode; published combined operating data apply to dynamically coupled circuit.

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

1938 Triadyne

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • PlateCurrentOutput

    45 mA

    ClassA;At 110 V

  • PlateCurrentInput

    7 mA

    ClassA;At 110 V

  • Load Resistance

    2000 ohm

    ClassA;At 110 V

  • Power Output

    2 W

    ClassA;At 110 V

  • Power Output

    3.8 W

    ClassA;At 180 V

Data set 02

195X General Electric Essential Characteristics

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Plate voltage

    180 V

    ClassA

  • Input-plate supply voltage

    100 V

    ClassA

  • Grid voltage

    0 V

    ClassA

  • Plate current

    46 mA

    ClassA

  • Input-plate current

    5.8 mA

    ClassA

  • Load resistance

    4000 ohm

    ClassA

  • Power output

    3.8 W

    ClassA

Data set 03

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

  • Input Plate Voltage

    100 V

    ClassA

Characteristic

  • Input Plate Current

    5.8 mA

    ClassA

SECTION 2

Triode

Other

  • Output Plate Voltage

    180 V

    ClassA

  • Load Resistance

    4000 ohm

    ClassA

  • Power Output

    3.8 W

    ClassA

Characteristic

  • Output Plate Current

    46 mA

    ClassA