What is the EF804S vacuum tube?

The EF804S is a pentode vacuum tube designed for preamp / microphone applications. Telefunken diamond. V72 preamp legend..

What is a EF804S substitute or equivalent?

Direct equivalents to the EF804S include None (unique pinout). 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 EF804S?

Amplification factor μ ≈ 38, transconductance gm ≈ 2 mA/V, plate resistance rp ≈ 2000.0 kΩ, max plate voltage 300 V, max plate dissipation 1 W, heater 6.3 V / 0.17 A.

Is the EF804S still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the EF804S as Collector 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 EF804S sound like?

Telefunken diamond. V72 preamp legend.. 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

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EF804S Pentode Vacuum Tube

Pentode6.3V / 0.17A9-pin Noval

SourceTelefunkenReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗

EF804S — Telefunken — pentode vacuum tube — (1951)

2000.0kΩ

2.0mA/V

4.3pF

0.1pF

5.50pF

GAIN38%

POWER3%

DRIVE0%

LINEARITY81%

SPECIFICATIONS

Heater6.3 V · 0.17 A

Max Plate Voltage300 V

Pa max1 W

Gain Factor38

gm2 mA/V

rp2000.0 kΩ

Inter-electrode capacitances

Cgk4.3 pF

Cgp0.06 pF

Cpk5.5 pF

Pinout9-pin Noval

Era1951

RarityCollector

HEATER6.3V / 0.17A

MAX PLATE300V / 1W

BASEnoval

Source datasheets

2 manufacturer datasheets cross-checked for EF804S

2 verified

EXECUTIVE SUMMARY

The EF804S is a indirectly-heated pentode from Telefunken, introduced around 1951. It provides a gain factor (μ) of 38 with 2000.0kΩ plate resistance. Commonly used in preamp / microphone applications. Telefunken diamond. V72 preamp legend.

APPLICATIONS

Voltage amplifier

Generic pentode preamp / microphone stage

HISTORY

Introduced1951ManufacturerTelefunken

Golden Age

EF804S Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

SPICE model not yet available. Loadline calculator requires calibrated Koren parameters.

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