What is the 6LF6 vacuum tube?

The 6LF6 is a tetrode vacuum tube designed for sweep / power applications. 40W sweep tube. Surpasses KT88 raw power..

What is a 6LF6 substitute or equivalent?

Direct equivalents to the 6LF6 include 6LW6, 6MH6. 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 6LF6?

Transconductance gm ≈ 16 mA/V, max plate voltage 990 V, max plate dissipation 40 W, heater 6.3 V / 2 A.

Is the 6LF6 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6LF6 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 6LF6 sound like?

40W sweep tube. Surpasses KT88 raw power.. 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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6LF6 Tetrode Vacuum Tube

Tetrode6.3V / 2A12-pin Compactron

SourceRadiomuseum 6LF6 beam powerReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Beam power tetrode rated at 40W for high-power output stages

Datasheet ↗

6LF6 — Sylvania·GE — tetrode vacuum tube — (1965)

16.0mA/V

37.0pF

3.0pF

18.50pF

GAIN0%

POWER100%

DRIVE50%

LINEARITY75%

SPECIFICATIONS

Heater6.3 V · 2 A

Max Plate Voltage990 V

Pa max40 W

Gain Factor—

gm16 mA/V

rp—

Inter-electrode capacitances

Cgk37 pF

Cgp3 pF

Cpk18.5 pF

Pinout12-pin Compactron

Era1965

RarityModerate

HEATER6.3V / 2A

MAX PLATE990V / 40W

BASEcompactron

Source datasheets

1 manufacturer datasheets cross-checked for 6LF6

1 verified

EXECUTIVE SUMMARY

The 6LF6 is a indirectly-heated beam tetrode from Sylvania·GE, introduced around 1965. Commonly used in sweep / power applications. 40W sweep tube. Surpasses KT88 raw power.

APPLICATIONS

High-power output

Generic tetrode sweep / power stage

• PA/public address

HISTORY

Introduced1965ManufacturerSylvania·GE

Late Production

6LF6 Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

SPICE model not yet available. Loadline calculator requires calibrated Koren parameters.

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