What is the 6AQ5 vacuum tube?

The 6AQ5 (6AQ5 / EL90) is a tetrode vacuum tube designed for power applications. Compact power..

What is a 6AQ5 substitute or equivalent?

Direct equivalents to the 6AQ5 include EL90, 6005. 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 6AQ5?

Amplification factor μ ≈ 10, transconductance gm ≈ 4.1 mA/V, plate resistance rp ≈ 52.0 kΩ, max plate voltage 250 V, max plate dissipation 12 W, heater 6.3 V / 0.45 A.

Is the 6AQ5 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6AQ5 as Common 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 6AQ5 sound like?

Compact power.. 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.

6AQ5 EL90 Tetrode Vacuum Tube

Also known as EL90 · 6005

Beam power tetrode rated at 12W for high-power output stages

TetrodeHeater 6.3 V · 0.45 A7-pin MiniatureRCA 1950

Plate dissipation: 12W
Max plate voltage: 250V
Max screen voltage: 275V
Max cathode current: 65mA
Transconductance: 4.1mA/V

6AQ5

Characteristics

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

HeaterIndirectly heated

Specifications of 6AQ5 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.45 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6AQ5 — Limiting values
Plate voltageVa max	250 V
Screen voltageVg2 max	275 V
Plate dissipationPa max	12 W
Screen dissipationPg2 max	2.2 W
Cathode currentIk max	65 mA
Grid resistorRg1 max	100 kΩ
Heater–cathode voltageVhk max	250 V

Mechanical

Specifications of 6AQ5 — Mechanical
Base	7-pin Miniature
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6AQ5 — Small signal
Transconductance	4.1 mA/V
Plate resistance	52 kΩ
Amplification factor	10

Capacitances

Specifications of 6AQ5 — Capacitances
Input	8 pF
Grid–plate	0.4 pF
Output	8.5 pF

Charactereditorial reading, not a measurement

Specifications of 6AQ5 — Character
Gain	10%
Power	30%
Drive	48%
Linearity	95%

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

Typical operation

Conditions published by the manufacturers, one row per condition. Nothing is computed.

Typical operation
Setup	Va	Vg2	Vg1 / Rk	Ia	Ig2	Load	Pout	THD	gm	rp	Source
triode connection, single-endedclass not stated	250 V			49.5 mA					4.5 mA/V		read on the sheet Lorenz · 1953 · transcript
Class A, single-endedpentode connection · fixed bias	180 V	180 V	-8.5 V	29 mA	3 mA	5.5 kΩ	2 W	8%	3.7 mA/V	58 kΩ	OCR, to be checked General Electric · 1951 · p. 2 · transcript
Class A, single-endedtriode connection	180 V			29 mA	3 mA	5.5 kΩ	2 W	8%	3.7 mA/V	58 kΩ	OCR, to be checked General Electric · 1954 · p. 2 · transcript
Class AB1, push-pullpentode connection · fixed bias	250 V	250 V	-15 V	70 mA	5 mA	10 kΩ a-a	10 W	5%			OCR, to be checked General Electric · 1951 · p. 2 · transcript

Using this tube

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : audit-us_a (CLEAN — matches canonical datasheet)Active model : Koren pentode

Manufacturer datasheets

8 manufacturer datasheets cross-checked for 6AQ5 / EL908 verified

Triode-connectedTung-Sol1956-1959 (Plate #5435 March 1, 1959 / Plate #4689 June 1, 1956)

µ: 0.5

6AQ5 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: audit-us_a (CLEAN — matches canonical datasheet)
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Koren pentode

Context

The 6AQ5 is a indirectly-heated beam tetrode from RCA, introduced around 1950. It provides a gain factor (μ) of 10 with 52.0kΩ plate resistance. Commonly used in power applications. Compact power.

History

Introduced: 1950
Manufacturer: RCA
Era: Golden Age

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