What is the 6AQ8 vacuum tube?

The 6AQ8 is a triode vacuum tube designed for preamp applications. Frame-grid. Sharp..

What is a 6AQ8 substitute or equivalent?

Direct equivalents to the 6AQ8 include ECC85. 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 6AQ8?

Amplification factor μ ≈ 57, transconductance gm ≈ 5.9 mA/V, plate resistance rp ≈ 9.7 kΩ, max plate voltage 300 V, max plate dissipation 2.5 W, heater 6.3 V / 0.435 A.

Is the 6AQ8 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6AQ8 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 6AQ8 sound like?

Frame-grid. Sharp.. 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

←6AQ8

← 6AQ5 6AS7G →Compare → ECC85

6AQ8 Triode Vacuum Tube

Dual triode6.3V / 0.435A9-pin NovalSPICE

SourcePhilips ECC85/6AQ8 datasheetReviewed2026-05-29StatusDataModelCalcModel2 enginesPDF

Medium-gain triode for driver and line stage applications

Datasheet ↗SPICE

6AQ8 — Philips — triode vacuum tube — (1958)

9.7kΩ

5.9mA/V

3.0pF

1.5pF

0.18pF

GAIN57%

POWER6%

DRIVE90%

LINEARITY72%

SPECIFICATIONS

Heater6.3 V · 0.435 A

Max Plate Voltage300 V

Pa max2.5 W

Gain Factor57

gm5.9 mA/V

rp9.7 kΩ

Inter-electrode capacitances

Cgk3 pF

Cgp1.5 pF

Cpk0.18 pF

Pinout9-pin Noval

Era1958

RarityModerate

HEATER6.3V / 0.435A

MAX PLATE300V / 2.5W

BASEnoval

SECTIONS2 (dual)

Source datasheets

2 manufacturer datasheets cross-checked for 6AQ8

2 verified

TYPICAL OPERATING POINT

SPICE model(2 available)3 .subckt available ↓

Va150V

Ia3.8mA

Vg-2V

Pd0.57W

RL19kΩ

Av32.7dB

EXECUTIVE SUMMARY

The 6AQ8 is a dual indirectly-heated triode from Philips, introduced around 1958. It provides a gain factor (μ) of 57 with 9700Ω plate resistance. Commonly used in preamp applications. Frame-grid. Sharp.

APPLICATIONS

Voltage amplifierHigh-gain preampPhase splitter

Generic triode preamp stage

• Hi-Fi stereo• Headphone amp• Studio/recording

VS ECC85

μ 0%Rp +0%Pd 0%Full comparison →

HISTORY

Introduced1958ManufacturerPhilips

Golden Age