What is the 6KD6 vacuum tube?

The 6KD6 is a tetrode vacuum tube designed for sweep / power applications. Big sweep tube. Tougher than KT88..

What is a 6KD6 substitute or equivalent?

Direct equivalents to the 6KD6 include 6LF6, 6LB6. 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 6KD6?

Amplification factor μ ≈ 4, transconductance gm ≈ 14 mA/V, plate resistance rp ≈ 6.0 kΩ, max plate voltage 990 V, max plate dissipation 33 W, heater 6.3 V / 2.85 A.

Is the 6KD6 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6KD6 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 6KD6 sound like?

Big sweep tube. Tougher than KT88.. 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.

6KD6 Tetrode Vacuum Tube

Also known as 6LF6 · 6LB6

Beam power tetrode rated at 33W for high-power output stages

TetrodeHeater 6.3 V · 2.85 A12-pin CompactronRCA·GE 1961

Plate dissipation: 33W
Max plate voltage: 990V
Transconductance: 14mA/V

6KD6

Characteristics

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

HeaterIndirectly heated

Specifications of 6KD6 — Heater
Heater voltageVh	6.3 V
Heater currentIh	2.85 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6KD6 — Limiting values
Plate voltageVa max	990 V
Plate dissipationPa max	33 W

Mechanical

Specifications of 6KD6 — Mechanical
Base	12-pin Compactron
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6KD6 — Small signal
Transconductance	14 mA/V
Plate resistance	6 kΩ
Amplification factor	4

Capacitances

Specifications of 6KD6 — Capacitances
Input	40 pF
Grid–plate	0.8 pF
Output	16 pF

Charactereditorial reading, not a measurement

Specifications of 6KD6 — Character
Gain	4%
Power	83%
Drive	94%
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	150 V	110 V	100 mA	2 mA	14 mA/V	OCR, to be checked General Electric · 1967 · p. 2 · transcript

Using this tube

No interactive loadline model for this tube yet — download a SPICE model below to simulate it in LTspice or ngspice.

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 6KD6 beam power

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 6KD62 verified

6KD6 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Radiomuseum 6KD6 beam power
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

The 6KD6 is a indirectly-heated beam tetrode from RCA·GE, introduced around 1961. It provides a gain factor (μ) of 4 with 6000Ω plate resistance. Commonly used in sweep / power applications. Big sweep tube. Tougher than KT88.

History

Introduced: 1961
Manufacturer: RCA·GE
Era: Late Production

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