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.

By Jean-Michel Falligan Devergne · Reviewed May 29, 2026

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6SJ7 Pentode Vacuum Tube

Pentode6.3V / 0.3AOctalSPICE

SourceRCA·SylvaniaReviewed2026-05-29StatusDataModelCalcModelKoren pentodePDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗SPICE

6SJ7 — RCA·Sylvania — pentode vacuum tube — (1938)

1000.0kΩ

1.6mA/V

6.0pF

0.0pF

7.00pF

GAIN19%

POWER6%

DRIVE0%

LINEARITY91%

SPECIFICATIONS

Heater6.3 V · 0.3 A

Max Plate Voltage300 V

Pa max2.5 W

Gain Factor19

gm1.65 mA/V

rp1000.0 kΩ

Inter-electrode capacitances

Cgk6 pF

Cgp0.005 pF

Cpk7 pF

PinoutOctal

Era1938

RarityCommon

HEATER6.3V / 0.3A

MAX PLATE300V / 2.5W

BASEoctal

Source datasheets

4 manufacturer datasheets cross-checked for 6SJ7

4 verified

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

Specs when the screen grid (g2) is tied to the anode — the tube acts as a triode.

According to RCA (Radio Corporation of America, Harrison, New Jersey) (1948 (June 15, 1948; courbes Oct 1947 - May 1948)): « Triode Connection »

EXECUTIVE SUMMARY

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.

APPLICATIONS

Voltage amplifier

Generic pentode preamp stage

HISTORY

Introduced1938ManufacturerRCA·Sylvania

Pre-War

6SJ7 Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

SIMILAR PENTODES

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