What is the 809 vacuum tube?

The 809 is a triode vacuum tube designed for transmitting applications. Compact transmitting triode..

What is a 809 substitute or equivalent?

Direct equivalents to the 809 include None. 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 809?

Amplification factor μ ≈ 50, transconductance gm ≈ 4.5 mA/V, plate resistance rp ≈ 11.0 kΩ, max plate voltage 1000 V, max plate dissipation 30 W, heater 6.3 V / 2.5 A.

Is the 809 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 809 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 809 sound like?

Compact transmitting triode.. 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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809 Triode Vacuum Tube

Triode6.3V / 2.5AUX-5SPICE

SourceRCA 809 datasheet · cap audit 2026-05-09Reviewed2026-05-29StatusDataModelCalcModelNorman KorenPDF

Power triode delivering 30W for push-pull and SET designs

Datasheet ↗SPICE

11.0kΩ

4.5mA/V

5.7pF

6.7pF

0.90pF

GAIN50%

POWER75%

DRIVE89%

LINEARITY75%

SPECIFICATIONS

Heater6.3 V · 2.5 A

Max Plate Voltage1000 V

Pa max30 W

Gain Factor50

gm4.5 mA/V

rp11.0 kΩ

Inter-electrode capacitances

Cgk5.7 pF

Cgp6.7 pF

Cpk0.9 pF

PinoutUX-5

Era1938

RarityModerate

HEATER6.3V / 2.5A

MAX PLATE1000V / 30W

BASEux5

Source datasheets

1 manufacturer datasheets cross-checked for 809

1 verified

TYPICAL OPERATING POINT

Va700V

Ia40.01mA

Vg-0.2V

Pd28.01W

RL3kΩ

Av19.9dB

EXECUTIVE SUMMARY

The 809 is a directly-heated triode from RCA, introduced around 1938. It provides a gain factor (μ) of 50 with 11.0kΩ plate resistance. Commonly used in transmitting applications. Compact transmitting triode.

APPLICATIONS

SET outputPush-pull output

Generic triode transmitting stage

• PA/public address

HISTORY

Introduced1938ManufacturerRCA

Pre-War

809 Datasheet

Local mirror · PDF

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