What is the 6BL7 vacuum tube?

The 6BL7 (6BL7GT) is a triode vacuum tube designed for driver applications. Medium mu twin triode. Punchy driver..

What is a 6BL7 substitute or equivalent?

Direct equivalents to the 6BL7 include 6BL7GTA. 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 6BL7?

Amplification factor μ ≈ 15, transconductance gm ≈ 7 mA/V, plate resistance rp ≈ 2.1 kΩ, max plate voltage 500 V, max plate dissipation 10 W, heater 6.3 V / 1.5 A.

Is the 6BL7 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6BL7 as Moderate 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 6BL7 sound like?

Medium mu twin triode. Punchy driver.. 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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6BL7 6BL7GT Triode Vacuum Tube

Dual triode6.3V / 1.5AOctalSPICE

SourceRCA·GE·SylvaniaReviewed2026-05-29StatusDataModelCalcModelAyumi NakabayashiPDF

Power triode delivering 10W for push-pull and SET designs

Datasheet ↗SPICE

6BL7GT — RCA·GE·Sylvania — triode vacuum tube — (1952)

2.1kΩ

7.0mA/V

4.2pF

6.0pF

0.90pF

GAIN15%

POWER25%

DRIVE98%

LINEARITY93%

SPECIFICATIONS

Heater6.3 V · 1.5 A

Max Plate Voltage500 V

Pa max10 W

Gain Factor15

gm7 mA/V

rp2.1 kΩ

Inter-electrode capacitances

Cgk4.2 pF

Cgp6 pF

Cpk0.9 pF

PinoutOctal

Era1952

RarityModerate

HEATER6.3V / 1.5A

MAX PLATE500V / 10W

BASEoctal

SECTIONS2 (dual)

Source datasheets

5 manufacturer datasheets cross-checked for 6BL7GT

5 verified

TYPICAL OPERATING POINT

Va425V

Ia17.3mA

Vg-23.3846052V

Pd7.35W

RL5kΩ

Av18.5dB

EXECUTIVE SUMMARY

The 6BL7 is a dual indirectly-heated triode from RCA·GE·Sylvania, introduced around 1952. It provides a gain factor (μ) of 15 with 2150Ω plate resistance. Commonly used in driver applications. Medium mu twin triode. Punchy driver.

APPLICATIONS

SET outputPush-pull outputPhase splitter

Generic triode driver stage

• Headphone amp

HISTORY

Introduced1952ManufacturerRCA·GE·Sylvania

Golden Age

6BL7 Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

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