What is the EL37 vacuum tube?

The EL37 is a pentode vacuum tube designed for power (pp) applications. Mullard flagship pentode. Massive gm..

What is a EL37 substitute or equivalent?

Direct equivalents to the EL37 include CV586. 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 EL37?

Amplification factor μ ≈ 10, transconductance gm ≈ 11 mA/V, plate resistance rp ≈ 13.5 kΩ, max plate voltage 400 V, max plate dissipation 25 W, heater 6.3 V / 1.4 A.

Is the EL37 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the EL37 as Rare 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 EL37 sound like?

Mullard flagship pentode. Massive gm.. 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

←EL37

← EL36 EL39 →Compare…

EL37 Pentode Vacuum Tube

Pentode6.3V / 1.4AOctal

SourceMullardReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Power pentode delivering up to 25W in pentode, UL, or triode mode

Datasheet ↗

EL37 — Mullard — pentode vacuum tube — (1946)

13.5kΩ

11.0mA/V

17.5pF

1.0pF

9.00pF

GAIN10%

POWER63%

DRIVE87%

LINEARITY95%

SPECIFICATIONS

Heater6.3 V · 1.4 A

Max Plate Voltage400 V

Pa max25 W

Gain Factor10

gm11 mA/V

rp13.5 kΩ

Inter-electrode capacitances

Cgk17.5 pF

Cgp1 pF

Cpk9 pF

PinoutOctal

Era1946

RarityRare

HEATER6.3V / 1.4A

MAX PLATE400V / 25W

BASEoctal

Source datasheets

2 manufacturer datasheets cross-checked for EL37

2 verified

EXECUTIVE SUMMARY

The EL37 is a indirectly-heated pentode from Mullard, introduced around 1946. It provides a gain factor (μ) of 10 with 13.5kΩ plate resistance. Commonly used in power (pp) applications. Mullard flagship pentode. Massive gm.

APPLICATIONS

Power output

Generic pentode power (pp) stage

HISTORY

Introduced1946ManufacturerMullard

Golden Age

EL37 Datasheet

Local mirror · PDF

↗

METRIX TESTER

Test this tube on a Metrix

SPICE model not yet available. Loadline calculator requires calibrated Koren parameters.

SIMILAR PENTODES

View all →

12SJ7Preamp 307APower/Output 310APreamp 35LR6Sweep / Power 47Power/Output 4P1LPower (SET output) — DHT pentode 5639Video / wideband (power)5654RF / Preamp