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7581A

Glass-octal beam-power tube designed for audio-frequency power amplification, including push-pull Class-A and Class-AB output service.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: -
Socket code: B9A
Base pins: 8
Nominal heater: 6.3 V / 900 mA

Description

Glass-octal beam power tube for audio-frequency power-amplifier applications, including push-pull Class A and AB service.

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: -
Socket code: B9A
Base pins: 8
Nominal heater voltage: 6.3 V
Nominal heater current: 900 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

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

Beam Power

X-ray radiationInterelectrode capacitances

Plate resistance: 33000 Ω
Transconductance: 0.0052 S
Max plate voltage: 450 V
Max screen voltage: 300 V
Max plate dissipation: 35 W
Max screen dissipation: 5 W

Promoted only from clearly labeled printed ratings/characteristics; specialized and operating data retained in parameter rows.

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

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Beam Power

Characteristic

TriodeConnectionAmplificationFactor
8
TriodeConnection
TriodeConnectionPlateResistance
1700 ohm
TriodeConnection
TriodeConnectionTransconductance
4700 uS
TriodeConnection

Data set 02

1966 Tung Sol Electronic Tubes 4 of 4

Published operating points and test conditions from this source.

SECTION 1

Beam Power

Characteristic

Grid
0.6 pf
PublishedTable
Voltage
0.6 VOLTS
PublishedTable
Heater
200 VOLTS
PublishedTable
Plate
45 VOLTS
PublishedTable
Screen
45 VOLTS
PublishedTable
Plate
35 WATTS
PublishedTable
Screen
5 WATTS
PublishedTable
With Cathode
5 MEGOHMS
PublishedTable
Plate
250 voLTs
PublishedTable
Grid #1 Voltage
-14 voLTs
PublishedTable
Plate
22500 OHMS
PublishedTable
Plate
72 MA
PublishedTable
Screen
5 MA
PublishedTable
Plate
25 VOLTS
PublishedTable
Grid
-2 VOLTS
PublishedTable
Peak
2 VOLTS
PublishedTable
Plate
1700 OHMS
PublishedTable
Zero—Signal Plate Current
4 MA
PublishedTable
Total Harmonic Distortion S
5 PERCENT
PublishedTable
Plate
35 VOLTS
PublishedTable

Other

Maximum—Signal Plate Current
44 MA
PublishedTable
Maximum —Signal Power Output
4 WATTS
PublishedTable

Data set 03

1968 General Electric Co

Published operating points and test conditions from this source.

SECTION 1

Beam Power

Other

Heater Voltage, ACor DC*. ... ..... . .63=06 Volts Base—B6-148, Short Medium-Shell Octal 6-Pin Micanol
6 Volts
Published datasheet; semantic line recovery
Grid-Number 1 to Plate: (gl top)........0.6 pf Maximum Over-all Length. .. ..... ... . .. 417 Inches
0.6 pf
Published datasheet; semantic line recovery
Output: pto (h+k-+b.p.+g2)............ 6.5 pf
6.5 pf
Published datasheet; semantic line recovery
Plate Voltage. . . ........... 500 450 Volts
450 Volts
Published datasheet; semantic line recovery
spect to Cathode. . . . ... 200 200 Volts
200 Volts
Published datasheet; semantic line recovery
Plate Dissipation. . .......... 35 35 Watts spect to Cathode. .. ....200 200 Volts
35 Watts
Published datasheet; semantic line recovery
Plate Dissipation. . .......... 35 35 Watts spect to Cathode. .. ....200 200 Volts
200 Volts
Published datasheet; semantic line recovery
Screen Dissipation. . .. ...... 5.0 Watts Grid-Number 1 Circuit Resistance
5 Watts
Published datasheet; semantic line recovery
Heater-Cathode Voltage With Fixed Bias. . ........ 0.1 0.1 Megohms
0.1 Megohms
Published datasheet; semantic line recovery
With Cathode Bias. ... . ... 0.5 0.5 Megohms
0.5 Megohms
Published datasheet; semantic line recovery
Plate Voltage . . . . . ... 70 Volts
70 Volts
Published datasheet; semantic line recovery
Screen Voltage . .. ... . L 300 Volts
300 Volts
Published datasheet; semantic line recovery
Grid-Number 1 Voltage. . . .. ... e Volts
1 Volt
Published datasheet; semantic line recovery
Plate Current. .. . .. 210 Milliamperes
210 Milliamperes
Published datasheet; semantic line recovery
Screen Current. . . .. .. 25 Milliamperes
25 Milliamperes
Published datasheet; semantic line recovery
Grid-Number 1 Voltage. .. . ... .. Volts
1 Volt
Published datasheet; semantic line recovery
Peak AF Grid-Number 1 Voltage. . . ... .. ... . . . . Volts
1 Volt
Published datasheet; semantic line recovery
Plate Voltage ... ... ... . . 250 300 350 Volts
350 Volts
Published datasheet; semantic line recovery
Screen Voltage. . ... .. .. 250 200 250 Volts
250 Volts
Published datasheet; semantic line recovery
Grid-Number 1 Voltage. .. . .. .. .. ... ... .. . —14 —12.5 —18 Volts
1 Volt
Published datasheet; semantic line recovery
Grid-Number 1 Voltage. .. . .. .. .. ... ... .. . —14 —12.5 —18 Volts
18 Volts
Published datasheet; semantic line recovery
Peak AF Grid-Number 1 Voltage . . .. .. ... ... ... .. .. . ... .. ... .... 14 12.5 18 Volts
1 Volt
Published datasheet; semantic line recovery
Peak AF Grid-Number 1 Voltage . . .. .. ... ... ... .. .. . ... .. ... .... 14 12.5 18 Volts
18 Volts
Published datasheet; semantic line recovery
Plate Resistance, approximate. . . .. ... .. ... .. ... ... ... ... 22500 35000 33000 Ohms
33000 Ohms
Published datasheet; semantic line recovery
Transconductance . . ... .. ... 6000 5300 5200 Micromhos
5200 Micromhos
Published datasheet; semantic line recovery
Zero-Signal Plate Current. ... . ... ... .. ... ... 72 48 54 Milliamperes
54 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Plate Current. ... ... ... .. ... ... ... .. .. ... ..... 79 55 66 Milliamperes
66 Milliamperes
Published datasheet; semantic line recovery
Zero-Signal Screen Current. . . .. ... . .. 5.0 2.5 2.5 Milliamperes
2.5 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Screen Current. . . .. ... .. .. ... 7.3 4.7 7.0 Milliamperes
7 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Power Output. ... .. ... .. ... ... 6.5 6.5 10.8 Watts
10.8 Watts
Published datasheet; semantic line recovery
Plate Voltage . . . .. ... 250 270 Volts
270 Volts
Published datasheet; semantic line recovery
Screen Voltage. . .. ... 250 270 Volts
270 Volts
Published datasheet; semantic line recovery
Grid-Number 1 Voltage. . . .. .. ... . —16 —17.5 Volts
1 Volt
Published datasheet; semantic line recovery
Grid-Number 1 Voltage. . . .. .. ... . —16 —17.5 Volts
17.5 Volts
Published datasheet; semantic line recovery
Peak AF Grid-to-Grid Voltage . . .. ... .. ... . 32 35 Volts
35 Volts
Published datasheet; semantic line recovery
Zero-Signal Plate Current. . ... ... . .. . . 120 134 Milliamperes
134 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Plate Current. .. ... .. ... . . ... .. ... 140 155 Milliamperes
155 Milliamperes
Published datasheet; semantic line recovery
Zero-Signal Screen Current. . . ... . 10 11 Milliamperes
11 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Screen Current. . ... ... L 16 17 Milliamperes
17 Milliamperes
Published datasheet; semantic line recovery
Effective Load Resistance, Plate-to-Plate.. . . ... ... ... . ... .. . ... .. ... .. ... ... 5000 5000 Ohms
5000 Ohms
Published datasheet; semantic line recovery
Maximum-Signal Power Qutput. . ... ... . 14.5 17.5 Watts
17.5 Watts
Published datasheet; semantic line recovery
Plate Voltage . . . ... .. . . 360 360 450 Volts
450 Volts
Published datasheet; semantic line recovery
Screen Voltage. . . ... ... 270 270 400 Volts
400 Volts
Published datasheet; semantic line recovery
Grid-Number 1 Voltage . . .. ... .. ... ... .. . ... .. ... —22.5 —22.5 —37 Volts
1 Volt
Published datasheet; semantic line recovery
Grid-Number 1 Voltage . . .. ... .. ... ... .. . ... .. ... —22.5 —22.5 —37 Volts
37 Volts
Published datasheet; semantic line recovery
Peak AF Grid-to-Grid Voltage . . . ... ... ... ... . ... ... ... ... ...... 45 45 70 Volts
70 Volts
Published datasheet; semantic line recovery
Zero-Signal Plate Current. .. .. .. ... .. ... .. ... 88 88 116 Milliamperes
116 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Plate Currenf. ... .. ... ... . . ... .. . . ... .. ... . ..... 132 140 210 Milliamperes
210 Milliamperes
Published datasheet; semantic line recovery
Zero-Signal Screen Current. . . ... ... 5.0 5.0 5.6 Milliamperes
5.6 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Screen Current. . . . ... ... ... ... ... ... 15 11 22 Milliamperes
22 Milliamperes
Published datasheet; semantic line recovery
Effective Load Resistance, Plate-to-Plate. . . . ... ... ... . ... ... . .. .. ... 6600 3800 5600 Ohms
5600 Ohms
Published datasheet; semantic line recovery
Maximum-Signal Power Output. . ... ... ... ... 26.5 18 55 Watts
55 Watts
Published datasheet; semantic line recovery
Plate Voltage . . . ... . e 360 360 Volts
360 Volts
Published datasheet; semantic line recovery
Screen Voltage. . ... ... . 225 270 Volts
270 Volts
Published datasheet; semantic line recovery
Grid-Number 1 Voltage. . . .. ... .. . e —18 —22.5 Volts
1 Volt
Published datasheet; semantic line recovery
Grid-Number 1 Voltage. . . .. ... .. . e —18 —22.5 Volts
22.5 Volts
Published datasheet; semantic line recovery
Peak AF Grid-to-Grid Voltage . . . . .. .. ... . . 52 72 Volts
72 Volts
Published datasheet; semantic line recovery
Zero-Signal Plate Current. .. .. . ... ... e 78 88 Milliamperes
88 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Plate Current... ... ... ... . .. ... 142 205 Milliamperes
205 Milliamperes
Published datasheet; semantic line recovery
Zero-Signal Screen Current. . . ... ... 3.5 5.0 Milliamperes
5 Milliamperes
Published datasheet; semantic line recovery
Maximum-Signal Screen Current. . . ... ... .. 11 16 Milliamperes
16 Milliamperes
Published datasheet; semantic line recovery
Effective Load Resistance, Plate-to-Plate. . . . .. ... ... . .. .. .. ... . ... ... . ... ... 6000 3800 Ohms
3800 Ohms
Published datasheet; semantic line recovery
1 Heater current of o bogey tube at Ef =6.3 volts.
6.3 volts
Published datasheet; semantic line recovery
€ The maximum screen voltage rating is 500 volts in push-pull circuits where the screen of each tube is connected to a
500 volts
Published datasheet; semantic line recovery

Data set 04

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Beam Power

Other

Peak Heater-Cathode Voltage
200 V
AbsoluteValue
Typical Plate Voltage
250 V
ClassA;PentodeConnection
Typical Screen Voltage
250 V
ClassA;PentodeConnection
Plate Current
72 mA
ClassA;PentodeConnection
Screen Current
5 mA
ClassA;PentodeConnection

Characteristic

Plate Resistance
22500 ohm
ClassA;PentodeConnection
Transconductance
6000 uS
ClassA;PentodeConnection
Triode Amplification Factor
8
TriodeConnection
Triode Plate Resistance
1700 ohm
TriodeConnection
Triode Transconductance
4700 uS
TriodeConnection

Data set 05

2026 Tungsol Rebrand

Published operating points and test conditions from this source.

SECTION 1

Beam Power

Other

Power Output
-
HI-FI audio output; Class A/push-pull data published