What is the EL509 vacuum tube?

The EL509 (EL509 / 6KG6) is a tetrode vacuum tube designed for power (se/pp) applications. High-power sweep pentode. Massive headroom..

What is a EL509 substitute or equivalent?

Direct equivalents to the EL509 include 6KG6. 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 EL509?

Amplification factor μ ≈ 10, transconductance gm ≈ 18 mA/V, plate resistance rp ≈ 8.0 kΩ, max plate voltage 700 V, max plate dissipation 35 W, heater 6.3 V / 2 A.

Is the EL509 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the EL509 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 EL509 sound like?

High-power sweep pentode. Massive headroom.. 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

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EL509 EL509 / 6KG6 Tetrode Vacuum Tube

Tetrode6.3V / 2AMagnoval + Top Cap

SourceFrank/pocnet EL509 datasheet · vacuumtubesinc · cap audit 2026-05-09Reviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Beam power tetrode rated at 35W for high-power output stages

Datasheet ↗

EL509 / 6KG6 — Philips·Svetlana — tetrode vacuum tube — (1963)

8.0kΩ

18.0mA/V

25.0pF

2.5pF

9.00pF

GAIN10%

POWER88%

DRIVE92%

LINEARITY95%

SPECIFICATIONS

Heater6.3 V · 2 A

Max Plate Voltage700 V

Pa max35 W

Gain Factor10

gm18 mA/V

rp8.0 kΩ

Inter-electrode capacitances

Cgk25 pF

Cgp2.5 pF

Cpk9 pF

PinoutMagnoval + Top Cap

Era1963

RarityModerate

HEATER6.3V / 2A

MAX PLATE700V / 35W

BASEmagnoval

Source datasheets

4 manufacturer datasheets cross-checked for EL509 / 6KG6

4 verified

EXECUTIVE SUMMARY

The EL509 is a indirectly-heated beam tetrode from Philips·Svetlana, introduced around 1963. It provides a gain factor (μ) of 10 with 8000Ω plate resistance. Commonly used in power (se/pp) applications. High-power sweep pentode. Massive headroom.

APPLICATIONS

High-power output

Generic tetrode power (se/pp) stage

• PA/public address

HISTORY

Introduced1963ManufacturerPhilips·Svetlana

Late Production

EL509 Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

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

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