What is the PX25-EmissionLabs vacuum tube?

The PX25-EmissionLabs (PX25 EML) is a triode vacuum tube designed for power (set) applications. Enhanced PX25..

What is a PX25-EmissionLabs substitute or equivalent?

Direct equivalents to the PX25-EmissionLabs 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 PX25-EmissionLabs?

Amplification factor μ ≈ 10, transconductance gm ≈ 8 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 PX25-EmissionLabs still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the PX25-EmissionLabs as Sought-after 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 PX25-EmissionLabs sound like?

Enhanced PX25.. 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

←PX25-EmissionLabs

← PX25 PX4 →Compare → PX25

PX25-EmissionLabs PX25 EML Triode Vacuum Tube

Triode4V / 2AUX-4SPICE

SourceEmission Labs design notes (EML-12B-20A-20B-30A) · external audit feedbackReviewed2026-05-29StatusDataModelCalcModelNorman KorenPDF

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

Datasheet ↗SPICE

PX25 EML — Emission Labs — triode vacuum tube — (2005)

1.3kΩ

8.0mA/V

11.4pF

14.8pF

8.30pF

GAIN10%

POWER63%

DRIVE99%

LINEARITY95%

SPECIFICATIONS

Heater4 V · 2 A

Max Plate Voltage400 V

Pa max25 W

Gain Factor10

gm8 mA/V

rp1.3 kΩ

Inter-electrode capacitances

Cgk11.4 pF

Cgp14.8 pF

Cpk8.3 pF

PinoutUX-4

Era2005

RaritySought-after

HEATER4V / 2A

MAX PLATE400V / 25W

BASEux4

Source datasheets

2 manufacturer datasheets cross-checked for PX25 EML

2 verified

TYPICAL OPERATING POINT

Va350V

Ia54.02mA

Vg-24.801854V

Pd18.91W

RL3kΩ

Av16.4dB

EXECUTIVE SUMMARY

The PX25-EmissionLabs is a directly-heated triode from Emission Labs, introduced around 2005. It provides a gain factor (μ) of 10 with 1265Ω plate resistance. Commonly used in power (set) applications. Enhanced PX25.

APPLICATIONS

SET outputPush-pull outputHeadphone output

Generic triode power (set) stage

• Hi-Fi stereo• Headphone amp

VS PX25

μ 0%Rp +0%Pd 0%Full comparison →

HISTORY

Introduced2005ManufacturerEmission Labs

Modern