What is the 6AU6 vacuum tube?

The 6AU6 is a pentode vacuum tube designed for preamp / rf applications. Sharp pentode preamp..

What is a 6AU6 substitute or equivalent?

Direct equivalents to the 6AU6 include EF94. 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 6AU6?

Amplification factor μ ≈ 36, transconductance gm ≈ 5.2 mA/V, plate resistance rp ≈ 1000.0 kΩ, max plate voltage 300 V, max plate dissipation 3 W, heater 6.3 V / 0.3 A.

Is the 6AU6 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6AU6 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 6AU6 sound like?

Sharp pentode preamp.. 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

←6AU6

← 6AS7GC 6BK5 →Compare → EF94

6AU6 Pentode Vacuum Tube

Pentode6.3V / 0.3A7-pin MiniatureSPICE

SourceRCAReviewed2026-05-29StatusDataModelCalcModelKoren pentodePDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗SPICE

6AU6 — RCA — pentode vacuum tube — (1950)

1000.0kΩ

5.2mA/V

5.5pF

0.0pF

5.00pF

GAIN36%

POWER8%

DRIVE0%

LINEARITY82%

SPECIFICATIONS

Heater6.3 V · 0.3 A

Max Plate Voltage300 V

Pa max3 W

Gain Factor36

gm5.2 mA/V

rp1000.0 kΩ

Inter-electrode capacitances

Cgk5.5 pF

Cgp0.0035 pF

Cpk5 pF

Pinout7-pin Miniature

Era1950

RarityCommon

HEATER6.3V / 0.3A

MAX PLATE300V / 3W

BASEminiature-7

Source datasheets

5 manufacturer datasheets cross-checked for 6AU6

5 verified

EXECUTIVE SUMMARY

The 6AU6 is a indirectly-heated pentode from RCA, introduced around 1950. It provides a gain factor (μ) of 36 with 1000.0kΩ plate resistance. Commonly used in preamp / rf applications. Sharp pentode preamp.

APPLICATIONS

Voltage amplifier

Generic pentode preamp / rf stage

VS EF94

Rp +0%Pd 0%Full comparison →

HISTORY

Introduced1950ManufacturerRCA

Golden Age