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.

WE408A 6028 Pentode Vacuum Tube

Also known as 6AK5 (20V heater) · 6028

Small-signal pentode for low-noise voltage amplification

PentodeHeater 20 V · 0.05 A7-pin MiniatureWestern Electric 1955

Plate dissipation: 1.7W
Max plate voltage: 180V
Transconductance: 5mA/V
Plate resistance: 340kΩ

WE408A

Characteristics

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

HeaterIndirectly heated

Specifications of WE408A — Heater
Heater voltageVh	20 V
Heater currentIh	0.05 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of WE408A — Limiting values
Plate voltageVa max	180 V
Plate dissipationPa max	1.7 W

Mechanical

Specifications of WE408A — Mechanical
Base	7-pin Miniature
Rarity	Rare
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of WE408A — Small signal
Transconductance	5 mA/V
Plate resistance	340 kΩ

Capacitances

Specifications of WE408A — Capacitances
Input	3.95 pF
Grid–plate	0.01 pF
Output	2.83 pF

Charactereditorial reading, not a measurement

Specifications of WE408A — Character
Gain	0%
Power	4%
Drive	0%
Linearity	75%

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

Voltage amplifier

Generic pentode preamp / hf stage

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026

Manufacturer datasheets

2 manufacturer datasheets cross-checked for WE408A / 60282 verified

WE408A DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Western Electric
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

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.

History

Introduced: 1955
Manufacturer: Western Electric
Era: Golden Age

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