What is the PP5/400 vacuum tube?

The PP5/400 is a triode vacuum tube designed for power (set) applications. British military..

What is a PP5/400 substitute or equivalent?

Direct equivalents to the PP5/400 include PX4. 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 PP5/400?

Amplification factor μ ≈ 9, transconductance gm ≈ 6 mA/V, plate resistance rp ≈ 1.5 kΩ, max plate voltage 400 V, max plate dissipation 25 W, heater 4 V / 2 A.

Is the PP5/400 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the PP5/400 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 PP5/400 sound like?

British military.. 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 29, 2026

←PP5/400

← PL504 PP6/400 →Compare → PX4

PP5/400 Triode Vacuum Tube

Triode4V / 2AUX-4SPICE

SourceMullard.org PX25/PP5-400 familyReviewed2026-05-29StatusDataModelCalcModelNorman KorenPDF

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

Datasheet ↗SPICE

PP5/400 — Osram — triode vacuum tube — (1935)

1.5kΩ

6.0mA/V

6.0pF

12.0pF

4.00pF

GAIN9%

POWER63%

DRIVE99%

LINEARITY95%

SPECIFICATIONS

Heater4 V · 2 A

Max Plate Voltage400 V

Pa max25 W

Gain Factor9

gm6 mA/V

rp1.5 kΩ

Inter-electrode capacitances

Cgk6 pF

Cgp12 pF

Cpk4 pF

PinoutUX-4

Era1935

RarityRare

HEATER4V / 2A

MAX PLATE400V / 25W

BASEux4

TYPICAL OPERATING POINT

Va350V

Ia59.37mA

Vg-25.76816V

Pd20.78W

RL3kΩ

Av16.4dB

EXECUTIVE SUMMARY

The PP5/400 is a directly-heated triode from Osram, introduced around 1935. It provides a gain factor (μ) of 9 with 1500Ω plate resistance. Commonly used in power (set) applications. British military.

APPLICATIONS

SET outputPush-pull outputHeadphone output

Generic triode power (set) stage

• Hi-Fi stereo• Headphone amp

VS PX4

μ +80%Rp +81%Pd +67%Full comparison →

HISTORY

Introduced1935ManufacturerOsram

Pre-War

PP5/400 Datasheet

Local mirror · PDF

↗

METRIX TESTER

Test this tube on a Metrix

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