What is the 4Y75R vacuum tube?

The 4Y75R is a tetrode vacuum tube designed for output power applications.

What is a 4Y75R substitute or equivalent?

Direct equivalents to the 4Y75R include EL156. 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 4Y75R?

Amplification factor μ ≈ 4, transconductance gm ≈ 10 mA/V, max plate voltage 800 V, max plate dissipation 35 W, heater 6.3 V / 1.65 A.

Is the 4Y75R still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 4Y75R 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 4Y75R 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

←4Y75R

← 4Y100R 50 →Compare → EL156

4Y75R Tetrode Vacuum Tube

Tetrode6.3V / 1.65AOctal

SourceMullardReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Beam power tetrode rated at 35W for high-power output stages

Datasheet ↗

4Y75R — Mullard — tetrode vacuum tube — (1960)

10.0mA/V

18.0pF

1.2pF

15.00pF

GAIN4%

POWER88%

DRIVE50%

LINEARITY95%

SPECIFICATIONS

Heater6.3 V · 1.65 A

Max Plate Voltage800 V

Pa max35 W

Gain Factor4

gm10 mA/V

rp—

Inter-electrode capacitances

Cgk18 pF

Cgp1.2 pF

Cpk15 pF

PinoutOctal

Era1960

RarityRare

HEATER6.3V / 1.65A

MAX PLATE800V / 35W

BASEoctal

Source datasheets

2 manufacturer datasheets cross-checked for 4Y75R

2 verified

EXECUTIVE SUMMARY

The 4Y75R is a indirectly-heated beam tetrode from Mullard, introduced around 1960. Commonly used in output power applications.

APPLICATIONS

High-power output

Generic tetrode output power stage

• PA/public address

VS EL156

Pd -30%Full comparison →

HISTORY

Introduced1960ManufacturerMullard

Late Production

4Y75R Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

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

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