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Voltage - Dual Triode (similar) ·Triode-Triode

12AT7

High-mu dual triode widely specified for RF and AF amplification, oscillators, and frequency-changing circuits, combining substantial transconductance with moderate plate resistance.

Directly heatedCold cathodeCommon cathodeDissimilar

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

Description

Twin triode for oscillator and AF/RF amplifier service; source also designates ECC81.

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: 10900 Ω
Transconductance: 0.0055 S
Amplification factor: 60
Max plate voltage: 300 V
Max plate dissipation: 2.5 W
Max cathode current: 18 mA

Each identical triode section.

Section 2

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 10900 Ω
Transconductance: 0.0055 S
Amplification factor: 60
Max plate voltage: 330 V
Max plate dissipation: 2.5 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
10900 ohm
Transconductance
5500 µS
Amplification Factor
60

Other

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

Data set 02

1958 Amperex Industrial

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Plate voltage
250 V
Published table
Plate current
10 mA
Published table

Characteristic

Transconductance
5500 µS
Published table
Amplification factor
55
Published table
Heater/filament voltage
6.3 V
Published rating
Heater/filament current
300 mA
Published rating
Series heater voltage
12.6 V
SeriesHeater
Series heater current
150 mA
SeriesHeater

Data set 03

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
MaximumFrequencyAsFrequencyChanger
500 MHz

Data set 04

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
FrequencyConverterMaximumFrequency
300 MHz

Data set 05

1961 Ferranti Technical Handbook

Published operating points and test conditions from this source.

SECTION 1

Triode

Application

Application
RF amplifier / frequency changer

Other

Maximum intended frequency
300 MHz

Data set 06

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Transconductance
5500 uS
HigherCurrentOperatingPoint

Data set 07

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
55
VoltageAmplifier
Transconductance
5500 µS
VoltageAmplifier
Series heater voltage
12.6 V
SeriesHeater

Other

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

Data set 08

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
Plate current
10 mA
ClassA

Characteristic

Plate resistance
10900 ohm
ClassA
Transconductance
5500 uS
ClassA
Amplification factor
60
ClassA

Data set 09

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
3.7 mA
Plate Resistance
15000 ohm
Transconductance
4000 uS
Amplification Factor
60

Other

Plate Voltage
100 V
EachUnit
Cathode Bias Resistance
270 ohm
EachUnit

Data set 10

1966 Tung Sol Electronic Tubes 2 of 4

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Plate voltage
250 V
ClassA;EachSection
Plate current
10 mA
ClassA;EachSection
Grid voltage
-12 V
ClassA;EachSection

Characteristic

Plate resistance
10900 ohm
ClassA;EachSection
Transconductance
5500 uS
ClassA;EachSection
Amplification factor
60
ClassA;EachSection

Capacitance

Grid-to-plate capacitance
1.7 pF
EachSection
Input capacitance
1.8 pF
EachSection

Data set 11

1968 General Electric Co

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Plate Voltage
250 V
EachSection
Amplification Factor
60
EachSection
Plate Resistance
10900 ohm
EachSection
Transconductance
5500 uS
EachSection

Data set 12

1968 Mazda Belvu

Published operating points and test conditions from this source.

SECTION 1

Triode

Application

Application
Oscillator_RF_AF_Amplifier text

Data set 13

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
2.8 W
Promoted published value

Characteristic

Plate resistance
10900 ohm
Promoted published value

Data set 14

1971 RCA HB3 Binder 5 of 7

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristics

Heater voltage series
12.6 V
SeriesHeater
Heater current series
150 mA
SeriesHeater
Heater voltage parallel
6.3 V
ParallelHeater
Heater current parallel
300 mA
ParallelHeater
Plate supply voltage
100 V
ClassA1;PublishedPoint1
Plate supply voltage
250 V
ClassA1;PublishedPoint2
Cathode-bias resistor
270 ohm
ClassA1;PublishedPoint1
Cathode-bias resistor
200 ohm
ClassA1;PublishedPoint2
Amplification factor
60
ClassA1

SECTION 2

Triode

Characteristics

Heater voltage series
12.6 V
SeriesHeater
Heater current series
150 mA
SeriesHeater
Heater voltage parallel
6.3 V
ParallelHeater
Heater current parallel
300 mA
ParallelHeater
Plate supply voltage
100 V
ClassA1;PublishedPoint1
Plate supply voltage
250 V
ClassA1;PublishedPoint2
Cathode-bias resistor
270 ohm
ClassA1;PublishedPoint1
Cathode-bias resistor
200 ohm
ClassA1;PublishedPoint2
Amplification factor
60
ClassA1
Plate resistance
15000 ohm
ClassA1;PublishedPoint1
Plate resistance
10900 ohm
ClassA1;PublishedPoint2
Transconductance
4000 µS
ClassA1;PublishedPoint1
Transconductance
5500 µS
ClassA1;PublishedPoint2
Plate current
3.7 mA
ClassA1;PublishedPoint1
Plate current
10 mA
ClassA1;PublishedPoint2

Other

Maximum plate voltage
300 V
ClassA1
Maximum plate dissipation
2.5 W
ClassA1
Maximum negative grid bias
50 V
ClassA1
Peak heater-cathode voltage
90 V

Capacitance

Grid-to-plate capacitance
1.5 pF
GridDrive
Grid-to-cathode capacitance
2.2 pF
GridDrive
Plate-to-cathode capacitance
0.4 pF
GridDrive
Heater-to-cathode capacitance
2.4 pF
GridDrive

Data set 15

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Heater Voltage (ac/dc) 12.6
6.3 V
Published in approved ECC81 target datasheet entry; Section1
Heater Current 0.15
300 mA
Published in approved ECC81 target datasheet entry; Section1

Capacitance

Grid to Cathode and Heater (Each unit)
2.2 pF
Published in approved ECC81 target datasheet entry; Section1
Unit No.l
0.5 pF
Published in approved ECC81 target datasheet entry; Section1
Unit No.2
0.4 pF
Published in approved ECC81 target datasheet entry; Section1
Cathode to Plate (Each unit)
0.2 pF
Published in approved ECC81 target datasheet entry; Section1
Cathode to Grid and Heater (Each unit)
4.6 pF
Published in approved ECC81 target datasheet entry; Section1
Plate to Grid and Heater (Each unit)
1.8 pF
Published in approved ECC81 target datasheet entry; Section1

Data set 16

2026 Genalex Rebrand

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Transconductance
4500 to 6500 µS
Plate 250 V; grid -2 V
Plate Current
9 to 12 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

Characteristics

Ua
250 V
Published value
Ia
10 mA
Published value
Ug
-2 V
Published value
S
5500 µS
Published value
µ
60
Published value
Ri
11 kΩ
Published value

Other

Ua
300 V
Published value
Wa
2.5 W
Published value
Ik
15 mA
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