What is the ECC85 vacuum tube?

The ECC85 is a triode vacuum tube designed for rf / preamp applications. VHF dual triode..

What is a ECC85 substitute or equivalent?

Direct equivalents to the ECC85 include 6AQ8. 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 ECC85?

Amplification factor μ ≈ 57, transconductance gm ≈ 6 mA/V, plate resistance rp ≈ 9.7 kΩ, max plate voltage 550 V, max plate dissipation 2.5 W, heater 6.3 V / 0.435 A.

Is the ECC85 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the ECC85 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 ECC85 sound like?

VHF dual triode.. 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.

ECC85 Triode Vacuum Tube

Also known as 6AQ8

Medium-gain triode for driver and line stage applications

Dual triodeHeater 6.3 V · 0.435 A9-pin Noval2 sectionsPhilips 1955

Plate dissipation: 2.5W
Max plate voltage: 550V
Amplification factor: 57
Transconductance: 6mA/V
Plate resistance: 9.7kΩ

ECC85

Characteristics

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

HeaterIndirectly heated

Specifications of ECC85 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.435 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of ECC85 — Limiting values
Plate voltageVa max	550 V
Plate dissipationPa max	2.5 W
Cathode currentIk max	15 mA
Grid resistorRg1 max	1 MΩ
Peak plate voltageVao	550 V
Heater–cathode voltageVhk max	90 V

Mechanical

Specifications of ECC85 — Mechanical
Base	9-pin Noval
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of ECC85 — Small signal
Transconductance	6 mA/V
Plate resistance	9.7 kΩ
Amplification factor	57

Capacitances

Specifications of ECC85 — Capacitances
Grid–cathode	3 pF
Grid–plate	1.5 pF
Plate–cathode	0.18 pF

Charactereditorial reading, not a measurement

Specifications of ECC85 — Character
Gain	57%
Power	6%
Drive	90%
Linearity	72%

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

Typical operation

Canonical operating pointModel

B+: 250 V
Load: 12 kΩ
Va: 150 V
Ia: 4.5 mA
Vg: -2.1 V
Pd: 0.68 W
Gain: 30.8 dB

At Q: Norman Koren
μ: 58.9
gm: 4.77 mA/V
rp: 12.4 kΩ

Design a stage →

Using this tube

Applications

Voltage amplifier
High-gain preamp
Phase splitter

Generic triode rf / preamp stage

Hi-Fi stereoHeadphone ampStudio/recording

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : Philips ECC85 datasheetActive model : Norman Koren

Manufacturer datasheets

7 manufacturer datasheets cross-checked for ECC857 verified

ECC85 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Philips ECC85 datasheet
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Norman Koren

Context

The ECC85 is a dual indirectly-heated triode from Philips, introduced around 1955. It provides a gain factor (μ) of 57 with 9700Ω plate resistance. Commonly used in rf / preamp applications. VHF dual triode.

History

Introduced: 1955
Manufacturer: Philips
Era: Golden Age

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