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6550A

Improved 6550-family beam tetrode for high-power audio amplification, intended for demanding push-pull output stages in high-fidelity and professional equipment.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: 7AC
Socket code: IO
Base pins: 8
Nominal heater: 6.3 V / 1.6 A

Description

Beam-power pentode designed for audio-frequency power amplifiers; rated for 42 W plate dissipation and push-pull outputs up to 100 W.

Socket description

International Octal

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 7AC
Socket code: IO
Base pins: 8
Nominal heater voltage: 6.3 V
Nominal heater current: 1.6 A
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

7AC - Terminal pinout

Electrical assignments shared by every tube using this base designation.

Terminal	Section	Connection	Evidence
PIN1Pin 1	—	NC	Verified 12L6GT/25L6GT manufacturer basing, 7AC
PIN2Pin 2	—	H — Heater	Verified 12L6GT/25L6GT manufacturer basing, 7AC
PIN3Pin 3	A	P — Plate (Anode)	Verified 12L6GT/25L6GT manufacturer basing, 7AC
PIN4Pin 4	A	G2 — Screen Grid	Verified 12L6GT/25L6GT manufacturer basing, 7AC
PIN5Pin 5	A	G1 — Control Grid	Verified 12L6GT/25L6GT manufacturer basing, 7AC
PIN7Pin 7	—	H — Heater	Verified 12L6GT/25L6GT manufacturer basing, 7AC
PIN8Pin 8	A	BP — Beam-Forming PlateGroup AC8	Verified 12L6GT/25L6GT manufacturer basing, 7AC
PIN8Pin 8	A	K — CathodeGroup AC8	Verified 12L6GT/25L6GT manufacturer basing, 7AC

Section ratings

1 physical section, each with unique specifications.

Section 1

Beam Power

X-ray radiationInterelectrode capacitances

Plate resistance: 15000 Ω
Transconductance: 0.011 S
Amplification factor: 8
Max plate voltage: 660 V
Max screen voltage: 440 V
Max plate dissipation: 42 W
Max screen dissipation: 6 W
Max cathode current: 190 mA

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

Beam Power

Characteristic

Grid-to-plate capacitance
0.8 pF
Input capacitance
5 pF
Output capacitance
10 pF

Other

Class A power output
20 W
ClassA