What is the 6SQ7 vacuum tube?

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

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.

6SQ7 Triode Vacuum Tube

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

TriodeHeater 6.3 V · 0.3 AOctalRCA 1938

Plate dissipation: 0.5W
Max plate voltage: 300V
Amplification factor: 100
Transconductance: 1.1mA/V
Plate resistance: 91kΩ

6SQ7

Characteristics

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

HeaterIndirectly heated

Specifications of 6SQ7 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.3 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6SQ7 — Limiting values
Plate voltageVa max	300 V
Plate dissipationPa max	0.5 W
Heater–cathode voltageVhk max	90 V

Mechanical

Specifications of 6SQ7 — Mechanical
Base	Octal
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6SQ7 — Small signal
Transconductance	1.1 mA/V
Plate resistance	91 kΩ
Amplification factor	100

Capacitances

Specifications of 6SQ7 — Capacitances
Grid–cathode	3.2 pF
Grid–plate	1.6 pF
Plate–cathode	3 pF

Charactereditorial reading, not a measurement

Specifications of 6SQ7 — Character
Gain	100%
Power	1%
Drive	9%
Linearity	50%

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

Typical operation

Canonical operating pointModel

B+: 250 V
Load: 182 kΩ
Va: 150 V
Ia: 0.84 mA
Vg: -1 V
Pd: 0.13 W
Gain: 36.7 dB

At Q: Norman Koren
μ: 98.2
gm: 1.22 mA/V
rp: 80.3 kΩ

Design a stage →

Using this tube

Applications

Voltage amplifier
High-gain preamp

Generic triode preamp stage

Hi-Fi stereoStudio/recording

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : RCA 6SQ7 datasheetActive model : Norman Koren

Manufacturer datasheets

5 manufacturer datasheets cross-checked for 6SQ75 verified

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

µ: 90

6SQ7 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: RCA 6SQ7 datasheet
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Norman Koren

Context

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.

History

Introduced: 1938
Manufacturer: RCA
Era: Pre-War

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