What is the 6SQ7 vacuum tube?

The 6SQ7 is a triode vacuum tube designed for preamp applications. High-mu detector..

What is a 6SQ7 substitute or equivalent?

Direct equivalents to the 6SQ7 include None. 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 6SQ7?

Amplification factor μ ≈ 100, transconductance gm ≈ 1.1 mA/V, plate resistance rp ≈ 91.0 kΩ, max plate voltage 300 V, max plate dissipation 0.5 W, heater 6.3 V / 0.3 A.

Is the 6SQ7 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6SQ7 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 6SQ7 sound like?

High-mu detector.. 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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6SQ7 Triode Vacuum Tube

Triode6.3V / 0.3AOctalSPICE

SourceRCA 6SQ7 datasheetReviewed2026-05-29StatusDataModelCalcModelNorman KorenPDF

High-gain dual triode — the standard for guitar and hi-fi preamps

Datasheet ↗SPICE

6SQ7 — RCA — triode vacuum tube — (1938)

100

91.0kΩ

1.1mA/V

3.2pF

1.6pF

3.00pF

GAIN100%

POWER1%

DRIVE9%

LINEARITY50%

SPECIFICATIONS

Heater6.3 V · 0.3 A

Max Plate Voltage300 V

Pa max0.5 W

Gain Factor100

gm1.1 mA/V

rp91.0 kΩ

Inter-electrode capacitances

Cgk3.2 pF

Cgp1.6 pF

Cpk3 pF

PinoutOctal

Era1938

RarityCommon

HEATER6.3V / 0.3A

MAX PLATE300V / 0.5W

BASEoctal

Source datasheets

5 manufacturer datasheets cross-checked for 6SQ7

5 verified

Triode-connectedRFT — VEB WERK FUR FERNMELDEWEAusgabe Juni 1953 (edition juin 1953)

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

According to RFT — VEB WERK FUR FERNMELDEWESEN (Berlin-Oberschöneweide), RDA/DDR (Ausgabe Juni 1953 (edition juin 1953)): « en Triode »

TYPICAL OPERATING POINT

Va150V

Ia0.84mA

Vg-1V

Pd0.13W

RL182kΩ

Av36.7dB

EXECUTIVE SUMMARY

The 6SQ7 is a indirectly-heated triode from RCA, introduced around 1938. It provides a gain factor (μ) of 100 with 91.0kΩ plate resistance. Commonly used in preamp applications. High-mu detector.

APPLICATIONS

Voltage amplifierHigh-gain preamp

Generic triode preamp stage

• Hi-Fi stereo• Studio/recording

HISTORY

Introduced1938ManufacturerRCA

Pre-War

6SQ7 Datasheet

Local mirror · PDF

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METRIX TESTER

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