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.

By Jean-Michel Falligan Devergne · Reviewed May 29, 2026

←304TL

← 300B-XLS-EmissionLabs 307A →Compare…

304TL 304TL / VT-129 Triode Vacuum Tube

Triode10V / 12.5ASpecial

SourceEimacReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

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

Datasheet ↗

304TL / VT-129 — Eimac — triode vacuum tube — (1938)

719Ω

16.7mA/V

12.1pF

8.6pF

0.80pF

GAIN12%

POWER100%

DRIVE99%

LINEARITY94%

SPECIFICATIONS

Heater10 V · 12.5 A

Max Plate Voltage3000 V

Pa max300 W

Gain Factor12

gm16.7 mA/V

rp719 Ω

Inter-electrode capacitances

Cgk12.1 pF

Cgp8.6 pF

Cpk0.8 pF

PinoutSpecial

Era1938

RarityRare

HEATER10V / 12.5A

MAX PLATE3000V / 300W

BASEspecial

Source datasheets

3 manufacturer datasheets cross-checked for 304TL / VT-129

3 verified

EXECUTIVE SUMMARY

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.

APPLICATIONS

SET outputPush-pull outputHeadphone output

Generic triode transmitting (set) stage

• Headphone amp• PA/public address

HISTORY

Introduced1938ManufacturerEimac

Pre-War

304TL Datasheet

Local mirror · PDF

↗

METRIX TESTER

Test this tube on a Metrix

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

SIMILAR TRIODES

View all →

01APreamp 100THTransmitting (SET)101DPower (SET)10YPower (SET)12AT7Driver 12AU7Line / Headphone 12AX7Preamp 12AY7Preamp