What is the ECF80 vacuum tube?

The ECF80 is a pentode vacuum tube designed for preamp applications.

What is a ECF80 substitute or equivalent?

Direct equivalents to the ECF80 include 6BL8. 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.

Is the ECF80 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the ECF80 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 ECF80 sound like?

Sonic character depends 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

ECF80 Pentode Vacuum Tube

Triode + Pentode6.3 V · 0.43 A9-pin Noval2 sectionsAlso known as6BL8

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : Philips ECF80 datasheet

ECF80

In brief

TriodeTriode

μ: 20
gm: 5 mA/V
rp: 4 kΩ
Pa: 1.5 W

PentodePentode

μ: 47
gm: 6.2 mA/V
rp: 400 kΩ
Pa: 1.7 W

The ECF80-T is a indirectly-heated triode from Philips, introduced around 1955. It provides a gain factor (μ) of 20 with 4000Ω plate resistance. Commonly used in preamp applications. Triode section. The ECF80-P is a indirectly-heated pentode from Philips, introduced around 1955. It provides a gain factor (μ) of 47 with 400.0kΩ plate resistance. Commonly used in preamp applications. Pentode section.

Limits

Specifications of ECF80
Specification	Value	Source
Heater
Heater voltage	6.3 V	Datasheet
Heater current	0.43 A	Datasheet

Specifications of ECF80-T — Triode
Specification	Value	Source
LimitsDatasheet maximum ratings — not to be exceeded
Max Plate V	250 V	Datasheet
Pa max	1.5 W	Datasheet

Typical operation

Canonical operating pointModel

B+: 225 V
Load: 8 kΩ
Va: 135 V
Ia: 8.7 mA
Vg: -5 V
Pd: 1.17 W
Gain: 23 dB

At Q: Norman Koren
μ: 17.7
gm: 3.57 mA/V
rp: 5 kΩ

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Using this tube

Open the loadline calculator

APPLICATIONS

Phase splitter

Generic pentode preamp stage

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Sources

Manufacturer datasheets

Triode

6 manufacturer datasheets cross-checked for ECF80 — Triode6 verified

Pentode

6 manufacturer datasheets cross-checked for ECF80 — Pentode6 verified

ECF80 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Philips ECF80 datasheet
Reviewed: 2026-05-29
Status: DataModelCalc
Model: SPICE model

Context

HISTORY

Introduced: 1955
Manufacturer: Philips
Era: Golden Age

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