Alternatives & variations Download PDF datasheet

Voltage - Dual Triode (similar) ·Triode-Triode

12AX7

High-mu twin triode designed for high-gain resistance-coupled AF amplification and phase inversion, also suitable for oscillator service; its amplification factor is approximately 100.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: 9A
Socket code: B9A
Base pins: 9
Nominal heater: 12.6 V / 150 mA

Description

High-mu twin triode for voltage amplification, phase inversion, oscillators, and multivibrators.

Socket description

Small-button Noval 9-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 9A
Socket code: B9A
Base pins: 9
Nominal heater voltage: 12.6 V
Nominal heater current: 150 mA
Parallel heater voltage: 6.3 V
Parallel heater current: 300 mA
Series capable: Yes

9A - Terminal pinout

Electrical assignments shared by every tube using this base designation.

Terminal	Section	Connection	Evidence
PIN12P	B	P — Plate (Anode) EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A
PIN22G1	B	G1 — Control Grid EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A
PIN32K	B	K — Cathode EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A
PIN4H	—	H — Heater EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A
PIN5H	—	H — Heater EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A
PIN61P	A	P — Plate (Anode) EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A
PIN71G1	A	G1 — Control Grid EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A
PIN81K	A	K — Cathode EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A
PIN9HCT	—	HCT — Heater Center Tap EIA transcription; manufacturer confirmation pending	Unverified EIA Base Connections, printed page 130, 9A

Section ratings

2 physical sections, each with unique specifications.

Section 1

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 62500 Ω
Transconductance: 0.0016 S
Amplification factor: 100
Max plate voltage: 330 V
Max plate dissipation: 1.1 W
Max cathode current: 9 mA

Each identical triode section.

Section 2

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 62500 Ω
Transconductance: 0.0016 S
Amplification factor: 100
Max plate voltage: 330 V
Max plate dissipation: 1.1 W

Published promoted values applied where semantically applicable; additional table values retained in section 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

1950 Sylvania

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Plate Resistance
62500 ohm
Transconductance
1600 µS
Amplification Factor
100

Other

Maximum Plate Voltage
330 V
Maximum Plate Dissipation
1.1 W
Heater Voltage Series
12.6 V
Heater Current Series
150 mA
Heater Voltage Parallel
6.3 V
Heater Current Parallel
300 mA

Data set 02

1953 RFT Rundfunk Technik

Published operating points and test conditions from this source.

SECTION 1

Triode

Application

Application
VoltageAmplifier text

Data set 03

1955 Marconi

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Series heater voltage
12.6 V
Series heater current
150 mA
Parallel heater voltage
6.3 V
Parallel heater current
300 mA
Maximum plate voltage
300 V
Maximum plate dissipation per section
1 W

Characteristic

Amplification factor
100
Transconductance
1600 uS

Capacitance

Grid-plate capacitance
1.7 pF
Grid-cathode capacitance
1.6 pF

Data set 04

1956 Amperex Hi Fi Brochure

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristics

Plate Voltage
100 V
Each section
Plate Current
0.5 mA
Each section
Control Grid Voltage
-1 V
Each section
Transconductance
1250 uS
PlateVoltage=100V
Plate Resistance
80000 ohm
PlateVoltage=100V
Plate Voltage
250 V
Each section
Plate Current
1.2 mA
Each section
Control Grid Voltage
-2 V
Each section

Other

Maximum Grid Resistance
2000000 ohm
Each section
Maximum Filament-to-Cathode Voltage
180 V

Data set 05

1958 Amperex Industrial

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Plate voltage
250 V
VoltageAmplifier
Grid voltage
-2 V
VoltageAmplifier
Plate current
1.2 mA
VoltageAmplifier

Characteristic

Amplification factor
100
Plate resistance
62500 ohm
Transconductance
1600 µS

Data set 06

1958 Brimar Radio Valve No 7

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Heater Voltage
12.6 V
Heater Current
150 mA

Data set 07

195X Tesla

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristics

Interelectrode capacitances
Published
See source sheet for electrode-specific capacitance values

Data set 08

1960 RCA Industrial and Communications Types

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

HeaterOrFilamentVoltage
12.6 V
HeaterOrFilamentCurrent
150 mA
Application
High-gain amplifier phase inverter oscillator

Data set 09

1961 Ferranti Technical Handbook

Published operating points and test conditions from this source.

SECTION 1

Triode

Application

Application
Resistance-coupled AF amplifier / phase inverter

Data set 10

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Plate Voltage
250 V

Characteristic

Plate Current
1.2 mA

Data set 11

1963 Amperex Condensed

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Heater voltage
6.3 V
Published heater rating
Heater current
300 mA
Published heater rating
Amplification factor
100
VoltageAmplifier
Plate resistance
62500 ohm
VoltageAmplifier
Transconductance
1600 µS
VoltageAmplifier
Series heater voltage
12.6 V
SeriesHeater
Series heater current
150 mA
SeriesHeater

Other

Plate voltage
250 V
VoltageAmplifier
Control-grid bias
-2 V
VoltageAmplifier
Plate current
1.2 mA
VoltageAmplifier

Data set 12

1965 Sylvania Electronic Tubes Vol3

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Heater voltage
12.6 V
Heater current
150 mA
Plate voltage
250 V
ClassA
Grid voltage
-2 V
ClassA
Plate current
1.2 mA
ClassA

Characteristic

Plate resistance
62500 ohm
ClassA
Transconductance
1600 uS
ClassA
Amplification factor
100
ClassA

Data set 13

1965 Westinghouse Data Book

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Heater Voltage
12.6 V
Heater Current
150 mA
Plate Current
0.5 mA
Plate Resistance
80000 ohm
Transconductance
1250 uS
Amplification Factor
100
Grid To Plate Capacitance
1.7 pF
Input Capacitance
1.6 pF

Other

Plate Voltage
100 V
EachUnit
Grid Voltage
-1 V
EachUnit

Data set 14

1968 General Electric Co

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Plate Voltage
250 V
EachSection
Amplification Factor
100
EachSection
Plate Resistance
62500 ohm
EachSection
Transconductance
1600 uS
EachSection

Data set 15

1971 RCA HB3 Binder 3 of 7

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Heater voltage
6.3 V
Nominal
Heater current
300 mA
Nominal
Heater voltage series
12.6 V
Series
Heater current series
150 mA
Series
Heater voltage parallel
6.3 V
Parallel
Heater current parallel
300 mA
Parallel
Maximum plate voltage
330 V
Promoted published value
Maximum plate dissipation
1.1 W
Promoted published value

Characteristic

Plate resistance
62500 ohm
Promoted published value
Transconductance
1600 uS
Promoted published value

Data set 16

2026 Genalex Rebrand

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Plate Current
1.05 to 2 mA
Plate 250 V; grid -2 V

Data set 17

2026 JJ Electronic

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Ik
8 mA
Published value

Characteristics

Ua
250 V
Published value
Ug
-2 V
Published value
Ia
1.2 mA
Published value
S
1600 µS
Published value
Ri
62.5 kΩ
Published value
µ
100
Published value

Capacitance

cg/k
1.6
Published value
ca
0.33
Published value
cg/a
1.7
Published value

Data set 18

2026 Mullard Rebrand

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristics

Heater current at 6.3 V
350 to 390 mA
Published min/max range
Heater current at 12.6 V
175 to 195 mA
Published min/max range