What is the 75TL vacuum tube?

The 75TL is a triode vacuum tube designed for transmitting (set) applications. Building block of the 304TL. Low mu power..

What are the key specifications of the 75TL?

Amplification factor μ ≈ 12, transconductance gm ≈ 3.35 mA/V, plate resistance rp ≈ 3.6 kΩ, max plate voltage 3000 V, max plate dissipation 75 W, heater 5 V / 6.25 A.

Is the 75TL still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 75TL 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 75TL sound like?

Building block of the 304TL. Low mu 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.

75TL Triode Vacuum Tube

Power triode delivering 75W for push-pull and SET designs

TriodeHeater 5 V · 6.25 AUX-4Eimac 1936

Plate dissipation: 75W
Max plate voltage: 3000V
Transconductance: 3.35mA/V

75TL

Characteristics

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

HeaterDirectly heated

Specifications of 75TL — Heater
Heater voltageVh	5 V
Heater currentIh	6.25 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 75TL — Limiting values
Plate voltageVa max	3000 V
Plate dissipationPa max	75 W

Mechanical

Specifications of 75TL — Mechanical
Base	UX-4
Rarity	Rare
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 75TL — Small signal
Transconductance	3.35 mA/V
Plate resistance	3.6 kΩ
Amplification factor	12

Capacitances

Specifications of 75TL — Capacitances
Grid–cathode	2.6 pF
Grid–plate	2.4 pF
Plate–cathode	0.4 pF

Charactereditorial reading, not a measurement

Specifications of 75TL — Character
Gain	12%
Power	100%
Drive	96%
Linearity	94%

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	THD	Source
triode connection, push-pullclass not stated · fixed bias	1500 V	-130 V	67 mA	3%	OCR, to be checked EIMAC · 1967 · p. 2 · transcript

Using this tube

No interactive loadline model for this tube yet — download a SPICE model below to simulate it in LTspice or ngspice.

Applications

SET output
Push-pull output

Generic triode transmitting (set) stage

PA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026

Manufacturer datasheets

3 manufacturer datasheets cross-checked for 75TL3 verified

75TL DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

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

Context

The 75TL is a directly-heated triode from Eimac, introduced around 1936. It provides a gain factor (μ) of 12 with 3582Ω plate resistance. Commonly used in transmitting (set) applications. Building block of the 304TL. Low mu power.

History

Introduced: 1936
Manufacturer: Eimac
Era: Pre-War

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