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.

6LF6 Tetrode Vacuum Tube

Also known as 6LW6 · 6MH6

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

TetrodeHeater 6.3 V · 2 A12-pin CompactronSylvania·GE 1965

Plate dissipation: 40W
Max plate voltage: 990V
Transconductance: 16mA/V

6LF6

Characteristics

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

HeaterIndirectly heated

Specifications of 6LF6 — Heater
Heater voltageVh	6.3 V
Heater currentIh	2 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6LF6 — Limiting values
Plate voltageVa max	990 V
Plate dissipationPa max	40 W

Mechanical

Specifications of 6LF6 — Mechanical
Base	12-pin Compactron
Rarity	Moderate
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6LF6 — Small signal
Transconductance	16 mA/V

Capacitances

Specifications of 6LF6 — Capacitances
Input	37 pF
Grid–plate	3 pF
Output	18.5 pF

Charactereditorial reading, not a measurement

Specifications of 6LF6 — Character
Gain	0%
Power	100%
Drive	50%
Linearity	75%

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

Using this tube

Interactive loadline calculator not available for this tube yet — it needs calibrated Koren or Ayumi parameters.

Applications

High-power output

Generic tetrode sweep / power stage

PA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : Radiomuseum 6LF6 beam power

Manufacturer datasheets

1 manufacturer datasheets cross-checked for 6LF61 verified

6LF6 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Radiomuseum 6LF6 beam power
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

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.

History

Introduced: 1965
Manufacturer: Sylvania·GE
Era: Late Production

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