What is the 45B-EmissionLabs vacuum tube?

The 45B-EmissionLabs (45B EML) is a triode vacuum tube designed for power (set) applications. Enhanced Type 45..

What is a 45B-EmissionLabs substitute or equivalent?

Direct equivalents to the 45B-EmissionLabs include 45. 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 45B-EmissionLabs?

Amplification factor μ ≈ 3.5, transconductance gm ≈ 2 mA/V, plate resistance rp ≈ 1.8 kΩ, max plate voltage 450 V, max plate dissipation 22 W, heater 2.5 V / 2.5 A.

Is the 45B-EmissionLabs still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 45B-EmissionLabs as Moderate 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 45B-EmissionLabs sound like?

Enhanced Type 45.. 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.

45B-EmissionLabs 45B EML Triode Vacuum Tube

Also known as 45

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

TriodeHeater 2.5 V · 2.5 AUX-4Emission Labs 2008

Plate dissipation: 22W
Max plate voltage: 450V
Transconductance: 2mA/V

45B-EmissionLabs

Characteristics

Datasheet values, once each. Every value cites its sheet.

HeaterDirectly heated

Specifications of 45B-EmissionLabs — Heater
Heater voltageVh	2.5 V
Heater currentIh	2.5 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 45B-EmissionLabs — Limiting values
Plate voltageVa max	450 V
Plate dissipationPa max	22 W

Mechanical

Specifications of 45B-EmissionLabs — Mechanical
Base	UX-4
Rarity	Moderate
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 45B-EmissionLabs — Small signal
Transconductance	2 mA/V
Plate resistance	1.8 kΩ
Amplification factor	3.5

Capacitances

Specifications of 45B-EmissionLabs — Capacitances
Grid–cathode	6 pF
Grid–plate	8 pF
Plate–cathode	3.5 pF

Charactereditorial reading, not a measurement

Specifications of 45B-EmissionLabs — Character
Gain	4%
Power	55%
Drive	98%
Linearity	95%

datasheet cited · model or editorial reading · catalogue value, no citation attached yet · nothing invented

Using this tube

Interactive loadline calculator not available for this tube yet — it needs calibrated Koren or Ayumi parameters.

Applications

SET output
Push-pull output
Headphone output

Generic triode power (set) stage

Hi-Fi stereoHeadphone amp

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 10, 2026Source : Emission Labs design notes (EML-12B-20A-20B-30A) · external audit feedback

Manufacturer datasheets

45B-EmissionLabs DatasheetFrank's Electron Tube Pages · PDF

SPICE models

Revision and verification status

Source: Emission Labs design notes (EML-12B-20A-20B-30A) · external audit feedback
Reviewed: 2026-05-10
Status: DataModelCalc
Model: under review

Context

The 45B-EmissionLabs is a directly-heated triode from Emission Labs, introduced around 2008. It provides a gain factor (μ) of 3.5 with 1750Ω plate resistance. Commonly used in power (set) applications. Enhanced Type 45.

History

Introduced: 2008
Manufacturer: Emission Labs
Era: Modern

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