What is the WE408A vacuum tube?

The WE408A (WE408A / 6028) is a pentode vacuum tube designed for preamp / hf applications. Sharp-cutoff pentode. 20V heater 6AK5..

What is a WE408A substitute or equivalent?

Direct equivalents to the WE408A include 6AK5 (20V heater), 6028. 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 WE408A?

Transconductance gm ≈ 5 mA/V, plate resistance rp ≈ 340.0 kΩ, max plate voltage 180 V, max plate dissipation 1.7 W, heater 20 V / 0.05 A.

Is the WE408A still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the WE408A 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 WE408A sound like?

Sharp-cutoff pentode. 20V heater 6AK5.. 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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WE408A WE408A / 6028 Pentode Vacuum Tube

Pentode20V / 0.05A7-pin Miniature

SourceWestern ElectricReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗

WE408A / 6028 — Western Electric — pentode vacuum tube — (1955)

340.0kΩ

5.0mA/V

4.0pF

0.0pF

2.83pF

GAIN0%

POWER4%

DRIVE0%

LINEARITY75%

SPECIFICATIONS

Heater20 V · 0.05 A

Max Plate Voltage180 V

Pa max1.7 W

Gain Factor—

gm5 mA/V

rp340.0 kΩ

Inter-electrode capacitances

Cgk3.95 pF

Cgp0.01 pF

Cpk2.83 pF

Pinout7-pin Miniature

Era1955

RarityRare

HEATER20V / 0.05A

MAX PLATE180V / 1.7W

BASEminiature-7

Source datasheets

2 manufacturer datasheets cross-checked for WE408A / 6028

2 verified

EXECUTIVE SUMMARY

The WE408A is a indirectly-heated pentode from Western Electric, introduced around 1955. Commonly used in preamp / hf applications. Sharp-cutoff pentode. 20V heater 6AK5.

APPLICATIONS

Voltage amplifier

Generic pentode preamp / hf stage

HISTORY

Introduced1955ManufacturerWestern Electric

Golden Age

WE408A Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

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

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