What is the 6CK4 vacuum tube?

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

What is a 6CK4 substitute or equivalent?

Direct equivalents to the 6CK4 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 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.

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

←6CK4

← 6CG7 6CY7 →Compare…

6CK4 Triode Vacuum Tube

Dual triode6.3V / 1.25A9-pin NovalSPICE

SourceRCA 6CK4 datasheet (NJ7P / vinylsavor)Reviewed2026-05-29StatusDataModelCalcModel2 enginesPDF

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

Datasheet ↗SPICE

6CK4 — RCA — triode vacuum tube — (1957)

1.2kΩ

5.5mA/V

8.0pF

6.5pF

1.80pF

GAIN7%

POWER30%

DRIVE99%

LINEARITY95%

SPECIFICATIONS

Heater6.3 V · 1.25 A

Max Plate Voltage550 V

Pa max12 W

Gain Factor7

gm5.5 mA/V

rp1.2 kΩ

Inter-electrode capacitances

Cgk8 pF

Cgp6.5 pF

Cpk1.8 pF

Pinout9-pin Noval

Era1957

RaritySought-after

HEATER6.3V / 1.25A

MAX PLATE550V / 12W

BASEoctal

SECTIONS2 (dual)

Source datasheets

3 manufacturer datasheets cross-checked for 6CK4

3 verified

TYPICAL OPERATING POINT

SPICE model(2 available)2 .subckt available ↓

Va250V

Ia40.12mA

Vg-27.99V

Pd10.03W

RL5kΩ

Av16.4dB

EXECUTIVE SUMMARY

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.

APPLICATIONS

SET outputPush-pull outputHeadphone outputPhase splitter

Generic triode driver stage

• Headphone amp

HISTORY

Introduced1957ManufacturerRCA

Golden Age

6CK4 Datasheet

Local mirror · PDF

↗

METRIX TESTER

Test this tube on a Metrix

SIMILAR TRIODES

View all →

01APreamp 100THTransmitting (SET)101DPower (SET)10YPower (SET)12AT7Driver 12AU7Line / Headphone 12AX7Preamp 12AY7Preamp