What is the 12SJ7 vacuum tube?

The 12SJ7 is a pentode vacuum tube designed for preamp applications. 12V version of 6SJ7..

What is a 12SJ7 substitute or equivalent?

Direct equivalents to the 12SJ7 include 6SJ7. 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 12SJ7?

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 12.6 V / 0.15 A.

Is the 12SJ7 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 12SJ7 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 12SJ7 sound like?

12V version of 6SJ7.. 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

←12SJ7

← 12E1 12SQ7 →Compare → 6SJ7

12SJ7 Pentode Vacuum Tube

Pentode12.6V / 0.15AOctalSPICE

Sourceaudit-us_a (CLEAN — matches canonical datasheet)Reviewed2026-05-29StatusDataModelCalcModelKoren pentodePDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗SPICE

12SJ7 — RCA — pentode vacuum tube — (1938)

1000.0kΩ

1.6mA/V

6.0pF

0.0pF

7.00pF

GAIN19%

POWER6%

DRIVE0%

LINEARITY91%

SPECIFICATIONS

Heater12.6 V · 0.15 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

HEATER12.6V / 0.15A

MAX PLATE300V / 2.5W

BASEoctal

Source datasheets

2 manufacturer datasheets cross-checked for 12SJ7

2 verified

EXECUTIVE SUMMARY

The 12SJ7 is a indirectly-heated pentode from RCA, introduced around 1938. It provides a gain factor (μ) of 19 with 1000.0kΩ plate resistance. Commonly used in preamp applications. 12V version of 6SJ7.

APPLICATIONS

Voltage amplifier

Generic pentode preamp stage

VS 6SJ7

μ 0%Rp +0%Pd 0%Full comparison →

HISTORY

Introduced1938ManufacturerRCA

Pre-War