What is the 6BQ6GTB vacuum tube?

The 6BQ6GTB is a tetrode vacuum tube designed for power applications. TV sweep repurposed..

What is a 6BQ6GTB substitute or equivalent?

Direct equivalents to the 6BQ6GTB include 6CU6. 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 6BQ6GTB?

Amplification factor μ ≈ 4, transconductance gm ≈ 5.9 mA/V, plate resistance rp ≈ 14.5 kΩ, max plate voltage 600 V, max plate dissipation 11 W, heater 6.3 V / 1.2 A.

Is the 6BQ6GTB still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6BQ6GTB 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 6BQ6GTB sound like?

TV sweep repurposed.. 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.

6BQ6GTB Tetrode Vacuum Tube

Also known as 6CU6

Beam power tetrode rated at 11W for high-power output stages

TetrodeHeater 6.3 V · 1.2 AOctalRCA 1955

Plate dissipation: 11W
Max plate voltage: 600V
Transconductance: 5.9mA/V

6BQ6GTB

Characteristics

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

HeaterIndirectly heated

Specifications of 6BQ6GTB — Heater
Heater voltageVh	6.3 V
Heater currentIh	1.2 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6BQ6GTB — Limiting values
Plate voltageVa max	600 V
Plate dissipationPa max	11 W

Mechanical

Specifications of 6BQ6GTB — Mechanical
Base	Octal
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6BQ6GTB — Small signal
Transconductance	5.9 mA/V
Plate resistance	14.5 kΩ
Amplification factor	4

Capacitances

Specifications of 6BQ6GTB — Capacitances
Input	15 pF
Grid–plate	0.6 pF
Output	7 pF

Charactereditorial reading, not a measurement

Specifications of 6BQ6GTB — Character
Gain	4%
Power	28%
Drive	86%
Linearity	95%

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

Typical operation

Conditions published by the manufacturers, one row per condition. Nothing is computed.

Typical operation
Setup	Va	Vg2	Ia	Ig2	gm	Source
pentode connection, single-endedclass not stated	250 V	150 V	57 mA	2.1 mA	5.9 mA/V	OCR, to be checked General Electric · 1957 · p. 2 · transcript

Using this tube

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

3 manufacturer datasheets cross-checked for 6BQ6GTB3 verified

6BQ6GTB 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 6BQ6GTB is a indirectly-heated beam tetrode from RCA, introduced around 1955. It provides a gain factor (μ) of 4 with 14.5kΩ plate resistance. Commonly used in power applications. TV sweep repurposed.

History

Introduced: 1955
Manufacturer: RCA
Era: Golden Age

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