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.

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

←4Y100R

← 4P1L 4Y75R →Compare → 1625

4Y100R Tetrode Vacuum Tube

Tetrode12.6V / 3.5AOctal

SourceMullardReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

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

Datasheet ↗

4Y100R — Mullard — tetrode vacuum tube — (1960)

550Ω

20.0mA/V

25.0pF

0.5pF

22.00pF

GAIN11%

POWER100%

DRIVE99%

LINEARITY95%

SPECIFICATIONS

Heater12.6 V · 3.5 A

Max Plate Voltage800 V

Pa max50 W

Gain Factor11

gm20 mA/V

rp550 Ω

Inter-electrode capacitances

Cgk25 pF

Cgp0.5 pF

Cpk22 pF

PinoutOctal

Era1960

RarityRare

HEATER12.6V / 3.5A

MAX PLATE800V / 50W

BASEoctal

Source datasheets

2 manufacturer datasheets cross-checked for 4Y100R

2 verified

EXECUTIVE SUMMARY

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.

APPLICATIONS

High-power output

Generic tetrode output power stage

• Headphone amp• PA/public address

VS 1625

μ +38%Pd +67%Full comparison →

HISTORY

Introduced1960ManufacturerMullard

Late Production

4Y100R Datasheet

Local mirror · PDF

↗