What is the 809 vacuum tube?

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

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.

809 Triode Vacuum Tube

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

TriodeHeater 6.3 V · 2.5 AUX-5RCA 1938

Plate dissipation: 30W
Max plate voltage: 1000V
Transconductance: 4.5mA/V

809

Characteristics

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

HeaterDirectly heated

Specifications of 809 — Heater
Heater voltageVh	6.3 V
Heater currentIh	2.5 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 809 — Limiting values
Plate voltageVa max	1000 V
Plate dissipationPa max	30 W

Mechanical

Specifications of 809 — Mechanical
Base	UX-5
Rarity	Moderate
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 809 — Small signal
Transconductance	4.5 mA/V
Plate resistance	11 kΩ
Amplification factor	50

Capacitances

Specifications of 809 — Capacitances
Grid–cathode	5.7 pF
Grid–plate	6.7 pF
Plate–cathode	0.9 pF

Charactereditorial reading, not a measurement

Specifications of 809 — Character
Gain	50%
Power	75%
Drive	89%
Linearity	75%

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

Typical operation

Conditions published by the manufacturers, one row per condition. Nothing is computed.

Typical operation
Setup	Va	Vg1 / Rk	Ia	Load	Source
Class B, push-pulltriode connection · fixed bias · values for two tubes	1000 V	-9 V	40 mA	11.6 kΩ a-a	OCR, to be checked RCA · 1946 · p. 1 · transcript

Model at this condition: Norman Koren Model
μ: 48.2
gm: 3.59 mA/V
rp: 13.4 kΩ

Using this tube

Applications

SET output
Push-pull output

Generic triode transmitting stage

PA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : RCA 809 datasheet · cap audit 2026-05-09Active model : Norman Koren

Manufacturer datasheets

1 manufacturer datasheets cross-checked for 8091 verified

809 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: RCA 809 datasheet · cap audit 2026-05-09
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Norman Koren

Context

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.

History

Introduced: 1938
Manufacturer: RCA
Era: Pre-War

METRIX TESTER