What is the 6K6GT vacuum tube?

The 6K6GT is a pentode vacuum tube designed for power (se) applications. Charming low-power SE..

What is a 6K6GT substitute or equivalent?

Direct equivalents to the 6K6GT include 41. 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 6K6GT?

Amplification factor μ ≈ 7, transconductance gm ≈ 2.3 mA/V, plate resistance rp ≈ 90.0 kΩ, max plate voltage 315 V, max plate dissipation 8.5 W, heater 6.3 V / 0.4 A.

Is the 6K6GT still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6K6GT as Common 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 6K6GT sound like?

Charming low-power SE.. 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.

6K6GT Pentode Vacuum Tube

Also known as 41

Small-signal pentode for low-noise voltage amplification

PentodeHeater 6.3 V · 0.4 AOctalRCA 1937

Plate dissipation: 8.5W
Max plate voltage: 315V
Transconductance: 2.3mA/V

6K6GT

Characteristics

Datasheet values, once each. Every value cites its sheet.

HeaterIndirectly heated

Specifications of 6K6GT — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.4 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6K6GT — Limiting values
Plate voltageVa max	315 V
Plate dissipationPa max	8.5 W

Mechanical

Specifications of 6K6GT — Mechanical
Base	Octal
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6K6GT — Small signal
Transconductance	2.3 mA/V
Plate resistance	90 kΩ
Amplification factor	7

Capacitances

Specifications of 6K6GT — Capacitances
Input	5.5 pF
Grid–plate	0.5 pF
Output	6 pF

Charactereditorial reading, not a measurement

Specifications of 6K6GT — Character
Gain	7%
Power	21%
Drive	10%
Linearity	95%

datasheet cited · model or editorial reading · catalogue value, no citation attached yet · nothing invented

Typical operation

Conditions published by the manufacturers, one row per condition. Nothing is computed.

Typical operation
Setup	Va	Vg2	Vg1 / Rk	Ia	Ig2	Load	Pout	THD	gm	μ	rp	Source
Class A, single-endedpentode connection · fixed bias	100 V	100 V	-7 V	9 mA	1.6 mA	12 kΩ	0.35 W	11%	1.5 mA/V			OCR, to be checked Hytron Corporation · 1938 · p. 3 · transcript
Class A, push-pulltriode connection · cathode bias	250 V			37.5 mA					2.7 mA/V	6.8	2.5 kΩ	OCR, to be checked General Electric · 1953 · p. 2 · transcript

Using this tube

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Active model : Koren pentode

Manufacturer datasheets

4 manufacturer datasheets cross-checked for 6K6GT4 verified

6K6GT DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: RCA
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Koren pentode

Context

The 6K6GT is a indirectly-heated pentode from RCA, introduced around 1937. It provides a gain factor (μ) of 7 with 90.0kΩ plate resistance. Commonly used in power (se) applications. Charming low-power SE.

History

Introduced: 1937
Manufacturer: RCA
Era: Pre-War

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