What is the 304TL vacuum tube?

The 304TL (304TL / VT-129) is a triode vacuum tube designed for transmitting (set) applications. Four 75TLs in one bottle. Colossal power..

What is a 304TL substitute or equivalent?

Direct equivalents to the 304TL include VT-129. 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 304TL?

Amplification factor μ ≈ 12, transconductance gm ≈ 16.7 mA/V, plate resistance rp ≈ 719 Ω, max plate voltage 3000 V, max plate dissipation 300 W, heater 10 V / 12.5 A.

Is the 304TL still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 304TL 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 304TL sound like?

Four 75TLs in one bottle. Colossal power.. 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.

304TL VT-129 Triode Vacuum Tube

Also known as VT-129

Power triode delivering 300W for push-pull and SET designs

TriodeHeater 10 V · 12.5 ASpecialEimac 1938

Plate dissipation: 300W
Max plate voltage: 3000V
Transconductance: 16.7mA/V

304TL

Characteristics

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

HeaterDirectly heated

Specifications of 304TL — Heater
Heater voltageVh	10 V
Heater currentIh	12.5 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 304TL — Limiting values
Plate voltageVa max	3000 V
Plate dissipationPa max	300 W

Mechanical

Specifications of 304TL — Mechanical
Base	Special
Rarity	Rare
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 304TL — Small signal
Transconductance	16.7 mA/V
Plate resistance	719 Ω
Amplification factor	12

Capacitances

Specifications of 304TL — Capacitances
Grid–cathode	12.1 pF
Grid–plate	8.6 pF
Plate–cathode	0.8 pF

Charactereditorial reading, not a measurement

Specifications of 304TL — Character
Gain	12%
Power	100%
Drive	99%
Linearity	94%

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

Using this tube

Interactive loadline calculator not available for this tube yet — it needs calibrated Koren or Ayumi parameters.

Applications

SET output
Push-pull output
Headphone output

Generic triode transmitting (set) stage

Headphone ampPA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026

Manufacturer datasheets

3 manufacturer datasheets cross-checked for 304TL / VT-1293 verified

304TL DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Eimac
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

The 304TL is a directly-heated triode from Eimac, introduced around 1938. It provides a gain factor (μ) of 12 with 719Ω plate resistance. Commonly used in transmitting (set) applications. Four 75TLs in one bottle. Colossal power.

History

Introduced: 1938
Manufacturer: Eimac
Era: Pre-War

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