What is the KT120 vacuum tube?

The KT120 is a tetrode vacuum tube designed for power (pp) applications. Modern high-power beam..

What is a KT120 substitute or equivalent?

Direct equivalents to the KT120 include KT88. 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 KT120?

Transconductance gm ≈ 12.5 mA/V, plate resistance rp ≈ 3.0 kΩ, max plate voltage 850 V, max plate dissipation 60 W, heater 6.3 V / 1.85 A.

Is the KT120 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the KT120 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 KT120 sound like?

Modern high-power beam.. 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.

KT120 Tetrode Vacuum Tube

Also known as KT88

Beam power tetrode rated at 60W for high-power output stages

TetrodeHeater 6.3 V · 1.85 AOctalTung-Sol 2009

Plate dissipation: 60W
Max plate voltage: 850V
Transconductance: 12.5mA/V

KT120

Characteristics

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

HeaterIndirectly heated

Specifications of KT120 — Heater
Heater voltageVh	6.3 V
Heater currentIh	1.85 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of KT120 — Limiting values
Plate voltageVa max	850 V
Plate dissipationPa max	60 W

Mechanical

Specifications of KT120 — Mechanical
Base	Octal
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of KT120 — Small signal
Transconductance	12.5 mA/V
Plate resistance	3 kΩ

Capacitances

Specifications of KT120 — Capacitances
Input	29 pF
Grid–plate	1.8 pF
Output	10 pF

Charactereditorial reading, not a measurement

Specifications of KT120 — Character
Gain	0%
Power	100%
Drive	97%
Linearity	75%

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

Using this tube

Applications

High-power output

Audio Research Reference 75PrimaLuna DiaLogue

PA/public address

Featured in these amplifiers

McIntosh MC275 →

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : audit-us_b (CLEAN — matches canonical datasheet)Active model : Koren pentode

Manufacturer datasheets

1 manufacturer datasheets cross-checked for KT1201 verified

KT120 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: audit-us_b (CLEAN — matches canonical datasheet)
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Koren pentode

Context

The KT120 is a indirectly-heated beam tetrode from Tung-Sol, introduced around 2009. Commonly used in power (pp) applications. Modern high-power beam.

History

Introduced: 2009
Manufacturer: Tung-Sol
Era: Modern

METRIX TESTER