What is the 6SJ7 vacuum tube?

The 6SJ7 is a pentode vacuum tube designed for preamp applications. Classic octal preamp pentode..

What is a 6SJ7 substitute or equivalent?

Direct equivalents to the 6SJ7 include EF37A. 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 6SJ7?

Amplification factor μ ≈ 19, transconductance gm ≈ 1.65 mA/V, plate resistance rp ≈ 1000.0 kΩ, max plate voltage 300 V, max plate dissipation 2.5 W, heater 6.3 V / 0.3 A.

Is the 6SJ7 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6SJ7 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 6SJ7 sound like?

Classic octal preamp pentode.. 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.

6SJ7 Pentode Vacuum Tube

Also known as EF37A

Small-signal pentode for low-noise voltage amplification

PentodeHeater 6.3 V · 0.3 AOctalRCA·Sylvania 1938

Plate dissipation: 2.5W
Max plate voltage: 300V
Amplification factor: 19
Transconductance: 1.65mA/V
Plate resistance: 1MΩ

6SJ7

Characteristics

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

HeaterIndirectly heated

Specifications of 6SJ7 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.3 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6SJ7 — Limiting values
Plate voltageVa max	300 V
Screen voltageVg2 max	125 V
Plate dissipationPa max	2.5 W
Screen dissipationPg2 max	0.3 W
Grid resistorRg1 max	2 MΩ
Heater–cathode voltageVhk max	100 V

Mechanical

Specifications of 6SJ7 — Mechanical
Base	Octal
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6SJ7 — Small signal
Transconductance	1.65 mA/V
Plate resistance	1 MΩ
Amplification factor	19

Capacitances

Specifications of 6SJ7 — Capacitances
Input	6 pF
Grid–plate	0.005 pF
Output	7 pF

Charactereditorial reading, not a measurement

Specifications of 6SJ7 — Character
Gain	19%
Power	6%
Drive	0%
Linearity	91%

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

Using this tube

Applications

Voltage amplifier

Generic pentode preamp stage

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Active model : Koren pentode

Manufacturer datasheets

4 manufacturer datasheets cross-checked for 6SJ74 verified

Triode-connectedRCA1948 (June 15, 1948; courbes Oct 1947 - May 1948)

µ: 2

6SJ7 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: RCA·Sylvania
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Koren pentode

Context

The 6SJ7 is a indirectly-heated pentode from RCA·Sylvania, introduced around 1938. It provides a gain factor (μ) of 19 with 1000.0kΩ plate resistance. Commonly used in preamp applications. Classic octal preamp pentode.

History

Introduced: 1938
Manufacturer: RCA·Sylvania
Era: Pre-War

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