What is the GK71 vacuum tube?

The GK71 (GK-71) is a pentode vacuum tube designed for transmitting applications. Russian transmitting pentode..

What is a GK71 substitute or equivalent?

Direct equivalents to the GK71 include None. These share the same pinout and operating envelope, so they can usually be swapped without circuit changes — though batch-to-batch variations between manufacturers (NOS vs current production) may shift the sonic character noticeably.

What are the key specifications of the GK71?

Amplification factor μ ≈ 5, transconductance gm ≈ 4 mA/V, max plate voltage 1500 V, max plate dissipation 125 W, heater 20 V / 3.1 A.

Is the GK71 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the GK71 as Moderate availability. NOS (new-old-stock) examples from RCA, Mullard, Tung-Sol, GE, Sylvania and Telefunken trade among collectors; modern production where it exists comes mostly from JJ Electronic, Electro-Harmonix, Tung-Sol (New Sensor), Genalex, and a handful of small-batch makers.

What does the GK71 sound like?

Russian transmitting pentode.. Sonic character also depends heavily on the circuit operating point, the surrounding tubes in the stage, and the output transformer when present — use the interactive loadline calculator on this page to explore the trade-offs.

By Jean-Michel Falligan Devergne · Reviewed May 29, 2026

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GK71 GK-71 Pentode Vacuum Tube

Pentode20V / 3.1ASpecial

SourceSoviet-Tubes ГК-71 datasheet · cap audit 2026-05-09Reviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Power pentode delivering up to 125W in pentode, UL, or triode mode

Datasheet ↗

GK-71 — Russian — pentode vacuum tube — (1960)

4.0mA/V

18.0pF

0.1pF

17.00pF

GAIN5%

POWER100%

DRIVE50%

LINEARITY95%

SPECIFICATIONS

Heater20 V · 3.1 A

Max Plate Voltage1500 V

Pa max125 W

Gain Factor5

gm4 mA/V

rp—

Inter-electrode capacitances

Cgk18 pF

Cgp0.15 pF

Cpk17 pF

PinoutSpecial

Era1960

RarityModerate

HEATER20V / 3.1A

MAX PLATE1500V / 125W

BASEspecial

Source datasheets

1 manufacturer datasheets cross-checked for GK-71

1 verified

EXECUTIVE SUMMARY

The GK71 is a indirectly-heated pentode from Russian, introduced around 1960. Commonly used in transmitting applications. Russian transmitting pentode.

APPLICATIONS

Power output

Generic pentode transmitting stage

• PA/public address

HISTORY

Introduced1960ManufacturerRussian

Late Production

GK71 Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

SPICE model not yet available. Loadline calculator requires calibrated Koren parameters.

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