7247

Dissimilar twin triode combining a high-mu voltage-amplifier section with a lower-mu, higher-current section, intended for audio and general amplifier circuits requiring two different gain characteristics.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: 9A
Socket code: B9A
Base pins: 9
Nominal heater: 6.3 V / 300 mA

Description

Dissimilar dual triode with high-mu and medium-mu units for first- and second-stage high-fidelity audio preamplification.

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: 6.3 V
Nominal heater current: 300 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

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: 1.2 W
Max cathode current: 22 mA

Section 1 high-mu values promoted from section-specific columns.

Section 2

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 7700 Ω
Transconductance: 0.0022 S
Amplification factor: 17
Max plate voltage: 330 V
Max plate dissipation: 3 W
Max cathode current: 22 mA

Section 2 low-mu values promoted from section-specific columns.

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

1968 General Electric Co

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristic

Plate Resistance
80000 ohm
Ep=100V
Transconductance
1250 uS
Ep=100V
Equivalent Noise and Hum Average
1.8 uV

SECTION 2

Triode

Characteristic

Plate Resistance
6500 ohm
Ep=100V
Transconductance
3100 uS
Ep=100V

Data set 02

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Peak Heater-Cathode Voltage
200 V
AbsoluteValue
Average Heater-Cathode Voltage
100 V
AbsoluteValue

Characteristic

Plate Voltage
250 V
ClassA
Amplification Factor
100
ClassA
Plate Resistance
62500 ohm
ClassA
Transconductance
1600 uS
ClassA
Plate Current
1.2 mA
ClassA

SECTION 2

Triode

Characteristic

Plate Voltage
250 V
ClassA
Amplification Factor
17
ClassA
Plate Resistance
7700 ohm
ClassA
Transconductance
2200 uS
ClassA
Plate Current
10.5 mA
ClassA