What is the EF86 vacuum tube?

The EF86 (EF86 / 6267) is a pentode vacuum tube designed for preamp applications. The audio preamp pentode..

What is a EF86 substitute or equivalent?

Direct equivalents to the EF86 include 6267, Z729. 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 EF86?

Amplification factor μ ≈ 38, transconductance gm ≈ 2.2 mA/V, plate resistance rp ≈ 2500.0 kΩ, max plate voltage 300 V, max plate dissipation 1 W, heater 6.3 V / 0.2 A.

Is the EF86 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the EF86 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 EF86 sound like?

The audio preamp 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.

EF86 6267 Pentode Vacuum Tube

Also known as 6267 · Z729

Small-signal pentode for low-noise voltage amplification

PentodeHeater 6.3 V · 0.2 A9-pin NovalMullard·Telefunken 1955

Plate dissipation: 1W
Max plate voltage: 300V
Amplification factor: 38
Transconductance: 2.2mA/V
Plate resistance: 2.5MΩ

EF86

Characteristics

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

HeaterIndirectly heated

Specifications of EF86 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.2 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of EF86 — Limiting values
Plate voltageVa max	300 V
Screen voltageVg2 max	200 V
Plate dissipationPa max	1 W
Screen dissipationPg2 max	0.2 W
Cathode currentIk max	6 mA
Grid resistorRg1 max	10 MΩ
Peak plate voltageVao	550 V

Mechanical

Specifications of EF86 — Mechanical
Base	9-pin Noval
Rarity	Sought-after
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of EF86 — Small signal
Transconductance	2.2 mA/V
Plate resistance	2.5 MΩ
Amplification factor	38

Capacitances

Specifications of EF86 — Capacitances
Input	3.8 pF
Grid–plate	0.05 pF
Output	5.3 pF

Charactereditorial reading, not a measurement

Specifications of EF86 — Character
Gain	38%
Power	3%
Drive	0%
Linearity	81%

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

Using this tube

Applications

Voltage amplifier

Vox AC15 preampLeak Stereo 20 preamp

Guitar amp

Featured in these amplifiers

Classic circuits

EF86 Pentode Preamp
Preamp Stage
EF86 low-noise pentode preamp stage. Used in Vox AC15/AC30 and many hi-fi phono stages. High gain with characteristic sparkle.
SEVb 250V · Vg -2V · Vg₂ 140V · RL 100kΩMullard EF86 Datasheet / Vox AC15 Schematic

Replace or compare

Sources

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

Manufacturer datasheets

6 manufacturer datasheets cross-checked for EF86 / 62676 verified

Triode-connectedMazda-Belvu1968 (date 1-68)

Vg1: -5 V
Ia: 4 mA
gm: 2 mA/V
µ: 33

EF86 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Mullard·Telefunken
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Koren pentode

Context

The EF86 (6267) is a small-signal pentode designed specifically for low-noise audio preamplifier service, with an internal shielding structure that minimizes hum and microphonics. It was the standard first-stage tube in high-end European hi-fi preamps and is the V1 tube in the Vox AC15 and AC30 Top Boost channels, defining their chimey, three-dimensional clean tone. With a voltage gain of approximately 200 in typical pentode operation, it provides more amplification than any dual triode but demands careful mechanical mounting to control microphonics. Mullard, Telefunken, and Amperex are the sought-after NOS makes; the tube's sensitivity to vibration remains its principal practical challenge in guitar amplifier service.

History

Introduced: 1955
Manufacturer: Mullard·Telefunken
Era: Golden Age

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