What is the ECC40 vacuum tube?

The ECC40 is a triode vacuum tube designed for preamp applications. Postwar Philips double triode on the side-contact B8A Rimlock base. Medium-mu (μ=32) sections built for AF voltage amplification, cascade gain stages, phase inversion, and the multivibrator / flip-flop service typical of late-1940s radio and counting circuits. Lower gain and stiffer plate than the later Noval ECC83, with a warmer, less etched top end and the soft, slightly hum-prone heater characteristic of the early rimlock generation..

What is a ECC40 substitute or equivalent?

Direct equivalents to the ECC40 include B339 (CV1382). 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 ECC40?

Amplification factor μ ≈ 32, transconductance gm ≈ 2.9 mA/V, plate resistance rp ≈ 11.0 kΩ, max plate voltage 300 V, max plate dissipation 1.5 W, heater 6.3 V / 0.6 A.

Is the ECC40 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the ECC40 as Sought-after 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 ECC40 sound like?

Postwar Philips double triode on the side-contact B8A Rimlock base. Medium-mu (μ=32) sections built for AF voltage amplification, cascade gain stages, phase inversion, and the multivibrator / flip-flop service typical of late-1940s radio and counting circuits. Lower gain and stiffer plate than the later Noval ECC83, with a warmer, less etched top end and the soft, slightly hum-prone heater characteristic of the early rimlock generation.. 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.

ECC40 (B339 (CV1382)) datasheet — pinout & specs

Characteristics

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

HeaterIndirectly heated

Specifications of ECC40 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.6 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of ECC40 — Limiting values
Plate voltageVa max	300 V
Plate dissipationPa max	1.5 W
Cathode currentIk max	10 mA
Peak plate voltageVao	550 V
Heater–cathode voltageVhk max	175 V (f−/k+) · 100 V (f+/k−)

Mechanical

Specifications of ECC40 — Mechanical
Base	8-pin Rimlock
Rarity	Sought-after
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of ECC40 — Small signal
Transconductance	2.9 mA/V
Plate resistance	11 kΩ
Amplification factor	32

Capacitances

Specifications of ECC40 — Capacitances
Grid–cathode	2.8 pF
Grid–plate	2.8 pF
Plate–cathode	1.1 pF

Charactereditorial reading, not a measurement

Specifications of ECC40 — Character
Gain	32%
Power	4%
Drive	89%
Linearity	84%

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

Typical operation

Canonical operating pointModel

B+: 250 V
Load: 22 kΩ
Va: 150 V
Ia: 6.34 mA
Vg: -3.5 V
Pd: 0.95 W
Gain: 27.7 dB

At Q: Norman Koren
μ: 33
gm: 4.65 mA/V
rp: 7.1 kΩ

Design a stage →

Using this tube

Applications

Voltage amplifier
Phase splitter

Generic triode preamp stage

Hi-Fi stereoHeadphone amp

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : Philips ECC40 datasheet (frank.pocnet.net)Active model : Norman Koren

Manufacturer datasheets

4 manufacturer datasheets cross-checked for ECC404 verified

ECC40 Datasheet5 variants · pick below

Manufacturer datasheets (PDF downloads)

Philips, Eindhoven

Philips sheets dated 1951.02.02, 1951.06.06, 1953.10.10; index page 1999.04.19 · 8 pp · EN · FR · DE · NL

Most complete manufacturer set: capacitances, applications, limiting values, two characteristic graphs, microphony note.

Philips English reprint

1966-11-11; page codes 7Z2 6996-7000 · 6 pp · EN

Quick reference, heating, pinout, typical point, output valve, push-pull, phase inverter, LF amplifier, limiting values, Ia/Va curves.

La Radiotechnique (Suresnes, Philips subsidiary)

12-1951 · 4 pp · FR

French nominal data, capacitances, BF amplifier table, limits, dimensions and both transfer/anode-curve graphs.

CIFTE / Mazda

I-1968 · 3 pp · FR

Nominal data, capacitances, pinout and anode-curve page; useful for late French/Mazda variant cross-check.

Philips Technical Article

Manufacturer-agnostic abstract · 1 pp · EN

Long-form descriptive article: general description, microphony guidance, AF amplifier use, output valve (SE + push-pull), three phase-inverter circuits (A/B/C), saw-tooth blocking oscillator, electronic counter flip-flop, with figure captions for curves 12-15.

Datasheet limits (full)

Va0 (cut-off plate V)

550 V

max, valve biased to cut-off

Va max

300 V

Pa max

1.5 W

Pg max

0.1 W

Ik max

10 mA

Rg max

1 MΩ

Vg @ Ig=+0.3 µA

-1.3 V

grid-current onset

Vhk max

175 V (f−/k+) · 100 V (f+/k−)

Rkf max

0.15 MΩ

heater–cathode loop

Bulb temp

120 °C

Cathode positive / filament negative: 175 V max. Cathode negative / filament positive: 100 V max. Bulb temperature limit from Philips/1966 only.

Per-section / per-manufacturer capacitances

Capacitance	Philips · Section I	Philips · Section II	Radiotechnique	CIFTE / Mazda
Cg	2.8 pF	2.6 pF	2.8 pF	—
Ca	1.1 pF	0.55 pF	1.1 pF	—
Cag	2.7 pF	2.8 pF	2.8 pF	—
Cgf	<0.1 pF	—	—	—
Ckf	3 pF	—	—	—
Ce	—	—	—	2.8 pF
Cs	—	—	—	1.1 pF
Cg_a	—	—	—	2.6 pF

Inter-section coupling: Caa_prime=<0.8 pF · Cgg_prime=<0.1 pF · Cag_prime=<0.1 pF · Ca_prime_g=<0.1 pF

Datasheet operating points

Class A · single triode output

Va250 V

Ia6 mA

Vg-5.6 V

Ra15 kΩ

Vi3.9 Vrms

Wo280 mW

dtot8.5 %

Philips p.2, 1966 p.2

Class A · push-pull (both sections)

Va250 V

Rk560 Ω

Raa30 kΩ

Vi max4.1 Vrms

Ia2 × 5.2–5.6 mA

Wo520 mW

dtot1 %

Philips p.2, 1966 p.2

Cascade 2-section · Vb=250 V

Vb250 V

Ra0.22 MΩ

Ra'0.1 MΩ

Itot2.5 mA

Gain× 740

Vo30 Vrms

dtot1.9 %

Philips p.3

Cascade 2-section · Vb=250 V

Vb250 V

Ra0.22 MΩ

Ra'0.22 MΩ

Itot2 mA

Gain× 780

Vo18 Vrms

dtot1.2 %

Philips p.3

LF voltage amplifier (Ra × Vb)

Rg = 1 MΩ · Rk and Rg′ scale with Ra · Ra 47k → Rk 1200 Ω, Rg′ 0.15 MΩ · Ra 100k → Rk 2200 Ω, Rg′ 0.33 MΩ · Ra 220k → Rk 3900 Ω, Rg′ 0.68 MΩ

Vb	Ra	Ia	Gain	Vo max	dtot
400 V	47 kΩ	4.1 mA	× 21	72 Vrms	4.4 %
350 V	47 kΩ	3.6 mA	× 20	60 Vrms	4.1 %
300 V	47 kΩ	3.1 mA	× 20	50 Vrms	4 %
250 V	47 kΩ	2.6 mA	× 20	40 Vrms	3.8 %
200 V	47 kΩ	2 mA	× 20	30 Vrms	3.4 %

Philips p.2/3, 1966 p.4

SPICE variants per manufacturer

Each card below is a named subcircuit inside the downloadable .subckt file. Same physical tube, different manufacturer / measurement convention. The Ampera loadline calculator uses the Philips/1953 family; copy the Koren line from any card into your own simulator to bias the engine the same way.

ECC40_TRIODE_PHILIPS_1953

Philips/Valvo high-gm

Va250 V

Vg-5.6 V

Ia6 mA

μ32

gm2.9 mA/V

rp11 kΩ

Cag2.7 pF

Koren fit

MU=31.92 EX=1.33 KG1=591.1 KP=1997.6 KVB=6269.5 VCT=0

Default for Philips 1950s sheets and 1966 English data.

ECC40_TRIODE_RT_1951

French Radiotechnique

Va250 V

Vg-5.5 V

Ia6 mA

μ30

gm2.7 mA/V

rp11 kΩ

Cag2.8 pF

Koren fit

MU=30 EX=1.33 KG1=634.9 KP=1997.6 KVB=6269.5 VCT=0

French documentation and conservative matching.

ECC40_TRIODE_MAZDA_CIFTE_1968

Late CIFTE/Mazda

Va250 V

Vg-5.5 V

Ia6 mA

μ30

gm2.7 mA/V

rp11 kΩ

Cag2.6 pF

Koren fit

MU=30 EX=1.33 KG1=634.9 KP=1997.6 KVB=6269.5 VCT=0

Use for Mazda-branded publication and lower Miller capacitance variant.

ECC40_TRIODE_1966

English 1966 issue (alias)

Va250 V

Vg-5.6 V

Ia6 mA

μ32

gm2.9 mA/V

rp11 kΩ

Koren fit

MU=31.92 EX=1.33 KG1=591.1 KP=1997.6 KVB=6269.5 VCT=0

Alias to PHILIPS_1953 for netlists that reference the 1966 sheet name.

Transfer curve comparison

Ia vs Vg at Va = 250 V — each manufacturer Koren fit overlaid. The de-rated French families (μ=30) read lower than the Philips/1966 high-gm family (μ=32) at the same grid voltage.

Philips/Valvo high-gmFrench Radiotechnique

Original descriptive texts

Verbatim excerpts from the four manufacturer datasheets. Expand each section to read the original text — the Philips technical article carries the richest application content.

SPICE models

Revision and verification status

Source: Philips ECC40 datasheet (frank.pocnet.net)
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Norman Koren

5 Koren fits

Context

The ECC40 is an indirectly heated double triode (6.3 V / 0.6 A) on the Philips B8A Rimlock 8-pin side-contact base, published 1951–1953 by Philips and reprinted in English through 1966. The two sections are wired with separate cathodes and share only the heater; the datasheet operating point is Va = 250 V, Vg ≈ −5.6 V, Ia = 6 mA per triode. Published parameters split into two manufacturer families: Philips/1966 give μ = 32, gm = 2.9 mA/V, rp = 11 kΩ; the French La Radiotechnique (1951) and CIFTE/Mazda (1968) editions publish μ = 30, gm = 2.7 mA/V at the same rp. Limits per triode are 300 V plate, 1.5 W plate dissipation, 10 mA cathode current, and an asymmetric 175 V (f−/k+) / 100 V (f+/k−) heater-to-cathode rating that earned the ECC40 its use in elevated-cathode phase inverters. The datasheet covers single-ended Class A output (280 mW into 15 kΩ at 8.5 % dtot), Class A push-pull (520 mW into 30 kΩ Raa at 1.0 % dtot), LF voltage amplification across Ra = 47 / 100 / 220 kΩ × Vb = 200…400 V, two-section cascade with gain 740–780, three phase-inverter circuits, and saw-tooth blocking-oscillator + flip-flop service for early electronic counters. The Rimlock base was retired in favour of the 9-pin Noval (ECC81/82/83) within a decade, which is why surviving NOS Philips, Mullard, Valvo and Mazda examples now read as collector pieces rather than a current-production part.

History

Introduced: 1948
Manufacturer: Philips·Mullard
Era: Golden Age

METRIX TESTER

ECC40 Triode Vacuum Tube