What is the 4Y100R vacuum tube?

The 4Y100R is a tetrode vacuum tube designed for output power applications.

What are the key specifications of the 4Y100R?

Amplification factor μ ≈ 11, transconductance gm ≈ 20 mA/V, plate resistance rp ≈ 550 Ω, max plate voltage 800 V, max plate dissipation 50 W, heater 12.6 V / 3.5 A.

Is the 4Y100R still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 4Y100R 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 4Y100R sound like?

Sonic character depends 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.

4Y100R Tetrode Vacuum Tube

Beam power tetrode rated at 50W for high-power output stages

TetrodeHeater 12.6 V · 3.5 AOctalMullard 1960

Plate dissipation: 50W
Max plate voltage: 800V
Transconductance: 20mA/V

4Y100R

Characteristics

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

HeaterIndirectly heated

Specifications of 4Y100R — Heater
Heater voltageVh	12.6 V
Heater currentIh	3.5 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 4Y100R — Limiting values
Plate voltageVa max	800 V
Plate dissipationPa max	50 W
Screen dissipationPg2 max	7.5 W
Grid resistorRg1 max	100 kΩ
Heater–cathode voltageVhk max	200 V

Mechanical

Specifications of 4Y100R — Mechanical
Base	Octal
Rarity	Rare

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 4Y100R — Small signal
Transconductance	20 mA/V
Plate resistance	550 Ω
Amplification factor	11

Capacitances

Specifications of 4Y100R — Capacitances
Input	25 pF
Grid–plate	0.5 pF
Output	22 pF

Charactereditorial reading, not a measurement

Specifications of 4Y100R — Character
Gain	11%
Power	100%
Drive	99%
Linearity	95%

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

High-power output

Generic tetrode output power stage

Headphone ampPA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 4Y100R2 verified

4Y100R DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

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

Context

The 4Y100R is a indirectly-heated beam tetrode from Mullard, introduced around 1960. It provides a gain factor (μ) of 11 with 550Ω plate resistance. Commonly used in output power applications.

History

Introduced: 1960
Manufacturer: Mullard
Era: Late Production

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