What is the 100TH vacuum tube?

The 100TH (100TH / VT-218) is a triode vacuum tube designed for transmitting (set) applications. High-mu Eimac transmitting triode. Needs power drive..

What is a 100TH substitute or equivalent?

Direct equivalents to the 100TH include VT-218. 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 100TH?

Amplification factor μ ≈ 38, transconductance gm ≈ 4.5 mA/V, plate resistance rp ≈ 8.4 kΩ, max plate voltage 3000 V, max plate dissipation 100 W, heater 5 V / 6.3 A.

Is the 100TH still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 100TH 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 100TH sound like?

High-mu Eimac transmitting triode. Needs power drive.. 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.

100TH VT-218 Triode Vacuum Tube

Also known as VT-218

Power triode delivering 100W for push-pull and SET designs

TriodeHeater 5 V · 6.3 AUX-4Eimac 1938

Plate dissipation: 100W
Max plate voltage: 3000V
Transconductance: 4.5mA/V

100TH

Characteristics

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

HeaterDirectly heated

Specifications of 100TH — Heater
Heater voltageVh	5 V
Heater currentIh	6.3 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 100TH — Limiting values
Plate voltageVa max	3000 V
Plate dissipationPa max	100 W

Mechanical

Specifications of 100TH — Mechanical
Base	UX-4
Rarity	Rare
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 100TH — Small signal
Transconductance	4.5 mA/V
Plate resistance	8.4 kΩ
Amplification factor	38

Capacitances

Specifications of 100TH — Capacitances
Grid–cathode	2.9 pF
Grid–plate	2 pF
Plate–cathode	0.3 pF

Charactereditorial reading, not a measurement

Specifications of 100TH — Character
Gain	38%
Power	100%
Drive	92%
Linearity	81%

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

Using this tube

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, 2026Source : Eimac 100TH datasheet (Eitel-McCullough, San Bruno CA)Active model : Ayumi Nakabayashi

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 100TH / VT-2182 verified

100TH DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Eimac 100TH datasheet (Eitel-McCullough, San Bruno CA)
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Ayumi Nakabayashi

Context

The 100TH is a directly-heated triode from Eimac, introduced around 1938. It provides a gain factor (μ) of 38 with 8400Ω plate resistance. Commonly used in transmitting (set) applications. High-mu Eimac transmitting triode. Needs power drive.

History

Introduced: 1938
Manufacturer: Eimac
Era: Pre-War

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