What is the VR40 vacuum tube?

The VR40 is a triode vacuum tube designed for power applications. Military PX25 variant..

What is a VR40 substitute or equivalent?

Direct equivalents to the VR40 include PX25. 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 VR40?

Amplification factor μ ≈ 9.5, transconductance gm ≈ 7.5 mA/V, plate resistance rp ≈ 1.3 kΩ, max plate voltage 400 V, max plate dissipation 25 W, heater 4 V / 2 A.

Is the VR40 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the VR40 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 VR40 sound like?

Military PX25 variant.. 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.

By Jean-Michel Falligan Devergne · Reviewed May 10, 2026

←VR40

← UY85 VT-103 →Compare → PX25

VR40 Triode Vacuum Tube

Triode4V / 2AUX-4SPICE

SourceMullard.org PX25/VR40 datasheetReviewed2026-05-10StatusDataModelCalcModelNorman KorenPDF

Power triode delivering 25W for push-pull and SET designs

Datasheet ↗SPICE

VR40 — Osram — triode vacuum tube — (1940)

9.5

1.3kΩ

7.5mA/V

5.5pF

9.0pF

4.50pF

GAIN10%

POWER63%

DRIVE99%

LINEARITY95%

SPECIFICATIONS

Heater4 V · 2 A

Max Plate Voltage400 V

Pa max25 W

Gain Factor9.5

gm7.5 mA/V

rp1.3 kΩ

Inter-electrode capacitances

Cgk5.5 pF

Cgp9 pF

Cpk4.5 pF

PinoutUX-4

Era1940

RarityRare

HEATER4V / 2A

MAX PLATE400V / 25W

BASEux4

TYPICAL OPERATING POINT

Va350V

Ia53.64mA

Vg-26.573415V

Pd18.78W

RL3kΩ

Av15.8dB

EXECUTIVE SUMMARY

The VR40 is a directly-heated triode from Osram, introduced around 1940. It provides a gain factor (μ) of 9.5 with 1265Ω plate resistance. Commonly used in power applications. Military PX25 variant.

APPLICATIONS

SET outputPush-pull outputHeadphone output

Generic triode power stage

• Hi-Fi stereo• Headphone amp

VS PX25

μ -5%Rp +0%Pd 0%Full comparison →

HISTORY

Introduced1940ManufacturerOsram

Pre-War