What is the EL91 vacuum tube?

The EL91 is a pentode vacuum tube designed for power applications. Small audio output..

What is a EL91 substitute or equivalent?

Direct equivalents to the EL91 include 6AM5. 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 EL91?

Amplification factor μ ≈ 12, transconductance gm ≈ 2.6 mA/V, plate resistance rp ≈ 130.0 kΩ, max plate voltage 250 V, max plate dissipation 4 W, heater 6.3 V / 0.2 A.

Is the EL91 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the EL91 as Moderate 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 EL91 sound like?

Small audio output.. 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

←EL91

← EL90 EL95 →Compare → 6888

EL91 Pentode Vacuum Tube

Pentode6.3V / 0.2A7-pin Miniature

Sourceaudit-eu_b (CLEAN — matches canonical datasheet)Reviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗

EL91 — Philips — pentode vacuum tube — (1950)

130.0kΩ

2.6mA/V

4.0pF

0.3pF

3.75pF

GAIN12%

POWER10%

DRIVE0%

LINEARITY94%

SPECIFICATIONS

Heater6.3 V · 0.2 A

Max Plate Voltage250 V

Pa max4 W

Gain Factor12

gm2.6 mA/V

rp130.0 kΩ

Inter-electrode capacitances

Cgk4 pF

Cgp0.3 pF

Cpk3.75 pF

Pinout7-pin Miniature

Era1950

RarityModerate

HEATER6.3V / 0.2A

MAX PLATE250V / 4W

BASEminiature-7

Source datasheets

4 manufacturer datasheets cross-checked for EL91

4 verified

Triode-connectedMullard1962 (MAY 1962)

Specs when the screen grid (g2) is tied to the anode — the tube acts as a triode.

250 V

Vg1

-13.5 V

18.3 mA

2.7 mA/V

18 Ω

Pout

1.7 W

According to Mullard (1962 (MAY 1962)): « Triode connection »

EXECUTIVE SUMMARY

The EL91 is a indirectly-heated pentode from Philips, introduced around 1950. It provides a gain factor (μ) of 12 with 130.0kΩ plate resistance. Commonly used in power applications. Small audio output.

APPLICATIONS

Voltage amplifier

Generic pentode power stage

VS 6888

μ +20%Pd -50%Full comparison →

HISTORY

Introduced1950ManufacturerPhilips

Golden Age