What is the 6CK4 vacuum tube?

The 6CK4 is a triode vacuum tube designed for driver applications. Audio driver classic..

What are the key specifications of the 6CK4?

Amplification factor μ ≈ 7, transconductance gm ≈ 5.5 mA/V, plate resistance rp ≈ 1.2 kΩ, max plate voltage 550 V, max plate dissipation 12 W, heater 6.3 V / 1.25 A.

Is the 6CK4 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6CK4 as Sought-after 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 6CK4 sound like?

Audio driver classic.. 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.

6CK4 Triode Vacuum Tube

Power triode delivering 12W for push-pull and SET designs

Dual triodeHeater 6.3 V · 1.25 A9-pin Noval2 sectionsRCA 1957

Plate dissipation: 12W
Max plate voltage: 550V
Transconductance: 5.5mA/V

6CK4

Characteristics

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

HeaterIndirectly heated

Specifications of 6CK4 — Heater
Heater voltageVh	6.3 V
Heater currentIh	1.25 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6CK4 — Limiting values
Plate voltageVa max	550 V
Plate dissipationPa max	12 W

Mechanical

Specifications of 6CK4 — Mechanical
Base	9-pin Noval
Rarity	Sought-after
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6CK4 — Small signal
Transconductance	5.5 mA/V
Plate resistance	1.2 kΩ
Amplification factor	7

Capacitances

Specifications of 6CK4 — Capacitances
Grid–cathode	8 pF
Grid–plate	6.5 pF
Plate–cathode	1.8 pF

Charactereditorial reading, not a measurement

Specifications of 6CK4 — Character
Gain	7%
Power	30%
Drive	99%
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	Vg1 / Rk	Ia	gm	μ	rp	Source
Class A, single-endedtriode connection · fixed bias	250 V	-28 V	40 mA	5.5 mA/V	6.6	1.2 kΩ	OCR, to be checked RCA · 1959 · p. 1 · transcript
triode connection, single-endedclass not stated · cathode bias	250 V	-28 V	40 mA	5.5 mA/V	6.6	1.2 kΩ	OCR, to be checked Tung-Sol · 1958 · p. 2 · transcript

SPICE model2 available

Model at this condition: Ayumi Nakabayashi · 2 engines Model
μ: 6.8
gm: 6.14 mA/V
rp: 1.1 kΩ

Using this tube

Applications

SET output
Push-pull output
Headphone output
Phase splitter

Generic triode driver stage

Headphone amp

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : RCA 6CK4 datasheet (NJ7P / vinylsavor)Active model : Ayumi Nakabayashi · 2 engines

Manufacturer datasheets

3 manufacturer datasheets cross-checked for 6CK43 verified

6CK4 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: RCA 6CK4 datasheet (NJ7P / vinylsavor)
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Ayumi Nakabayashi · 2 engines

Context

The 6CK4 is a dual indirectly-heated triode from RCA, introduced around 1957. It provides a gain factor (μ) of 7 with 1200Ω plate resistance. Commonly used in driver applications. Audio driver classic.

History

Introduced: 1957
Manufacturer: RCA
Era: Golden Age

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