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.

12SJ7 Pentode Vacuum Tube

Also known as 6SJ7

Small-signal pentode for low-noise voltage amplification

PentodeHeater 12.6 V · 0.15 AOctalRCA 1938

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

12SJ7

Characteristics

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

HeaterIndirectly heated

Specifications of 12SJ7 — Heater
Heater voltageVh	12.6 V
Heater currentIh	0.15 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 12SJ7 — Limiting values
Plate voltageVa max	300 V
Plate dissipationPa max	2.5 W

Mechanical

Specifications of 12SJ7 — Mechanical
Base	Octal
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 12SJ7 — Small signal
Transconductance	1.65 mA/V
Plate resistance	1 MΩ
Amplification factor	19

Capacitances

Specifications of 12SJ7 — Capacitances
Input	6 pF
Grid–plate	0.005 pF
Output	7 pF

Charactereditorial reading, not a measurement

Specifications of 12SJ7 — 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, 2026Source : audit-us_a (CLEAN — matches canonical datasheet)Active model : Koren pentode

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 12SJ72 verified

12SJ7 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: audit-us_a (CLEAN — matches canonical datasheet)
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Koren pentode

Context

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.

History

Introduced: 1938
Manufacturer: RCA
Era: Pre-War

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