What is the 300B-XLS-EmissionLabs vacuum tube?

The 300B-XLS-EmissionLabs (300B-XLS EML) is a triode vacuum tube designed for power (set) applications. Enhanced dissipation 300B..

What is a 300B-XLS-EmissionLabs substitute or equivalent?

Direct equivalents to the 300B-XLS-EmissionLabs include 300B family — check bias and dissipation envelope before substitution; XLS is uprated and not a blind drop-in in every 300B circuit. 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 300B-XLS-EmissionLabs?

Amplification factor μ ≈ 4, transconductance gm ≈ 5.5 mA/V, plate resistance rp ≈ 700 Ω, max plate voltage 450 V, max plate dissipation 40 W, heater 5 V / 1.2 A.

Is the 300B-XLS-EmissionLabs still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 300B-XLS-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 300B-XLS-EmissionLabs sound like?

Enhanced dissipation 300B.. 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

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300B-XLS-EmissionLabs 300B-XLS EML Triode Vacuum Tube

Triode5V / 1.2AUX-4

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

High-power directly-heated triode for single-ended amplification

Datasheet ↗

300B-XLS EML — Emission Labs — triode vacuum tube — (2010)

700Ω

5.5mA/V

8.5pF

15.0pF

4.10pF

GAIN4%

POWER100%

DRIVE99%

LINEARITY95%

SPECIFICATIONS

Heater5 V · 1.2 A

Max Plate Voltage450 V

Pa max40 W

Gain Factor4

gm5.5 mA/V

rp700 Ω

Inter-electrode capacitances

Cgk8.5 pF

Cgp15 pF

Cpk4.1 pF

PinoutUX-4

Era2010

RaritySought-after

HEATER5V / 1.2A

MAX PLATE450V / 40W

BASEux4

Source datasheets

2 manufacturer datasheets cross-checked for 300B-XLS EML

2 verified

EXECUTIVE SUMMARY

The 300B-XLS-EmissionLabs is a directly-heated triode from Emission Labs, introduced around 2010. It provides a gain factor (μ) of 4 with 700Ω plate resistance. Commonly used in power (set) applications. Enhanced dissipation 300B.

APPLICATIONS

SET outputPush-pull outputHeadphone output

Generic triode power (set) stage

• Hi-Fi stereo• Headphone amp• PA/public address

HISTORY

Introduced2010ManufacturerEmission Labs

Modern

300B-XLS-EmissionLabs Datasheet

Frank's Electron Tube Pages · PDF

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METRIX TESTER

Test this tube on a Metrix

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

SIMILAR TRIODES

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01APreamp 100THTransmitting (SET)101DPower (SET)10YPower (SET)12AT7Driver 12AU7Line / Headphone 12AX7Preamp 12AY7Preamp