What is the EF94 vacuum tube?

The EF94 (EF94 / 6AU6) is a pentode vacuum tube designed for preamp / if amp applications. European designation of the 6AU6 sharp-cutoff preamp/IF pentode..

What is a EF94 substitute or equivalent?

Direct equivalents to the EF94 include 6AU6, 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 EF94?

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 EF94 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the EF94 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 EF94 sound like?

European designation of the 6AU6 sharp-cutoff preamp/IF pentode.. 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.

EF94 6AU6 Pentode Vacuum Tube

Also known as 6AU6 · EF94

Small-signal pentode for low-noise voltage amplification

PentodeHeater 6.3 V · 0.3 A7-pin MiniaturePhilips·Mullard 1950

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

EF94

Characteristics

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

HeaterIndirectly heated

Specifications of EF94 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.3 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of EF94 — Limiting values
Plate voltageVa max	300 V
Plate dissipationPa max	3 W

Mechanical

Specifications of EF94 — Mechanical
Base	7-pin Miniature
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of EF94 — Small signal
Transconductance	5.2 mA/V
Plate resistance	1 MΩ

Capacitances

Specifications of EF94 — Capacitances
Input	5.5 pF
Grid–plate	0.0035 pF
Output	5 pF

Charactereditorial reading, not a measurement

Specifications of EF94 — Character
Gain	0%
Power	8%
Drive	0%
Linearity	75%

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

Using this tube

Applications

Voltage amplifier

Generic pentode preamp / if amp stage

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : Mullard EF94 / RCA 6AU6 datasheetActive model : Koren pentode

Manufacturer datasheets

1 manufacturer datasheets cross-checked for EF94 / 6AU61 verified

EF94 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Mullard EF94 / RCA 6AU6 datasheet
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Koren pentode

Context

The EF94 is a indirectly-heated pentode from Philips·Mullard, introduced around 1950. Commonly used in preamp / if amp applications. European designation of the 6AU6 sharp-cutoff preamp/IF pentode.

History

Introduced: 1950
Manufacturer: Philips·Mullard
Era: Golden Age

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