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.

6AU6 Pentode Vacuum Tube

Also known as EF94

Small-signal pentode for low-noise voltage amplification

PentodeHeater 6.3 V · 0.3 A7-pin MiniatureRCA 1950

Plate dissipation: 3W
Max plate voltage: 300V
Amplification factor: 36
Transconductance: 5.2mA/V
Plate resistance: 1MΩ

6AU6

Characteristics

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

HeaterIndirectly heated

Specifications of 6AU6 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.3 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6AU6 — Limiting values
Plate voltageVa max	300 V
Screen voltageVg2 max	150 V
Plate dissipationPa max	3 W
Screen dissipationPg2 max	0.65 W
Heater–cathode voltageVhk max	250 V

Mechanical

Specifications of 6AU6 — Mechanical
Base	7-pin Miniature
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6AU6 — Small signal
Transconductance	5.2 mA/V
Plate resistance	1 MΩ
Amplification factor	36

Capacitances

Specifications of 6AU6 — Capacitances
Input	5.5 pF
Grid–plate	0.0035 pF
Output	5 pF

Charactereditorial reading, not a measurement

Specifications of 6AU6 — Character
Gain	36%
Power	8%
Drive	0%
Linearity	82%

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

Using this tube

Applications

Voltage amplifier

Generic pentode preamp / rf stage

Replace or compare

Sources

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

Manufacturer datasheets

5 manufacturer datasheets cross-checked for 6AU65 verified

6AU6 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

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

Context

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.

History

Introduced: 1950
Manufacturer: RCA
Era: Golden Age

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