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.

ECF80 Pentode Vacuum Tube

Also known as 6BL8

Triode + PentodeHeater 6.3 V · 0.43 A9-pin Noval2 sectionsPhilips 1955

Triode · Plate dissipation: 1.5W
Triode · Amplification factor: 20
Pentode · Plate dissipation: 1.7W
Pentode · Amplification factor: 47

ECF80

Characteristics

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

HeaterIndirectly heated

Specifications of ECF80 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.43 A

Mechanical

Specifications of ECF80 — Mechanical
Base	9-pin Noval
Rarity	Common
Pinout

TriodeTriode

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of ECF80-T — Triode — Limiting values
Plate voltageVa max	250 V
Screen voltageVg2 max	175 V
Plate dissipationPa max	1.5 W
Cathode currentIk max	14 mA
Grid resistorRg1 max	1 MΩ
Peak plate voltageVao	550 V

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of ECF80-T — Triode — Small signal
Transconductance	5 mA/V
Plate resistance	4 kΩ
Amplification factor	20

Capacitances

Specifications of ECF80-T — Triode — Capacitances
Grid–cathode	2.5 pF
Grid–plate	1.5 pF
Plate–cathode	1.8 pF

Charactereditorial reading, not a measurement

Specifications of ECF80-T — Triode — Character
Gain	20%
Power	4%
Drive	96%
Linearity	90%

PentodePentode

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of ECF80-P — Pentode — Limiting values
Plate voltageVa max	250 V
Screen voltageVg2 max	175 V
Plate dissipationPa max	1.7 W
Screen dissipationPg2 max	0.5 W
Cathode currentIk max	14 mA
Grid resistorRg1 max	1 MΩ
Peak plate voltageVao	550 V
Heater–cathode voltageVhk max	100 V

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of ECF80-P — Pentode — Small signal
Transconductance	6.2 mA/V
Plate resistance	400 kΩ
Amplification factor	47

Capacitances

Specifications of ECF80-P — Pentode — Capacitances
Input	5.2 pF
Grid–plate	0.025 pF
Output	3.4 pF

Charactereditorial reading, not a measurement

Specifications of ECF80-P — Pentode — Character
Gain	47%
Power	4%
Drive	0%
Linearity	77%

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

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

Design a stage →

Using this tube

Applications

Phase splitter

Generic pentode preamp stage

Replace or compare

Sources

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

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

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.

History

Introduced: 1955
Manufacturer: Philips
Era: Golden Age

METRIX TESTER

Characteristics

HeaterIndirectly heated

Mechanical

TriodeTriode

Limiting valuesDatasheet maximum ratings — not to be exceeded

Small signalDatasheet parameters at the reference operating point — not limits

Capacitances

Charactereditorial reading, not a measurement?

PentodePentode

Limiting valuesDatasheet maximum ratings — not to be exceeded

Small signalDatasheet parameters at the reference operating point — not limits

Capacitances

Charactereditorial reading, not a measurement?

Typical operation

Using this tube

Applications

Replace or compare

Versus 12SJ7

Similar tubes

Sources

Manufacturer datasheets

SPICE models

Context

History

Test this tube on a Metrix

Charactereditorial reading, not a measurement

Charactereditorial reading, not a measurement