What is the NR47 vacuum tube?

The NR47 is a triode vacuum tube designed for power applications. European DHT..

What is a NR47 substitute or equivalent?

Direct equivalents to the NR47 include PX25 class. 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 NR47?

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 NR47 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the NR47 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 NR47 sound like?

European DHT.. 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

←NR47

← KT99 Nuvistor 7587 →Compare…

NR47 Triode Vacuum Tube

Triode4V / 2AUX-4SPICE

SourceMullard.org PX25/NR47 familyReviewed2026-05-10StatusDataModelCalcModelNorman KorenPDF

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

Datasheet ↗SPICE

NR47 — Various — triode vacuum tube — (1940)

9.5

1.3kΩ

7.5mA/V

5.0pF

8.0pF

4.00pF

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 pF

Cgp8 pF

Cpk4 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 NR47 is a directly-heated triode from Various, introduced around 1940. It provides a gain factor (μ) of 9.5 with 1265Ω plate resistance. Commonly used in power applications. European DHT.

APPLICATIONS

SET outputPush-pull outputHeadphone output

Generic triode power stage

• Hi-Fi stereo• Headphone amp

HISTORY

Introduced1940ManufacturerVarious

Pre-War

NR47 Datasheet

Frank's Electron Tube Pages · PDF

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METRIX TESTER

Test this tube on a Metrix

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