What is the KT170 vacuum tube?

The KT170 is a tetrode vacuum tube designed for power (pp) applications. Largest KT. Massive headroom..

What is a KT170 substitute or equivalent?

Direct equivalents to the KT170 include KT150 (larger). 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 KT170?

Transconductance gm ≈ 14 mA/V, max plate voltage 900 V, max plate dissipation 85 W, heater 6.3 V / 1.97 A.

Is the KT170 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the KT170 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 KT170 sound like?

Largest KT. Massive headroom.. 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.

KT170 Tetrode Vacuum Tube

Also known as KT150 (larger)

Beam power tetrode rated at 85W for high-power output stages

TetrodeHeater 6.3 V · 1.97 AOctalTung-Sol 2020

Plate dissipation: 85W
Max plate voltage: 900V
Transconductance: 14mA/V

KT170

Characteristics

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

HeaterIndirectly heated

Specifications of KT170 — Heater
Heater voltageVh	6.3 V
Heater currentIh	1.97 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of KT170 — Limiting values
Plate voltageVa max	900 V
Plate dissipationPa max	85 W

Mechanical

Specifications of KT170 — Mechanical
Base	Octal
Rarity	Moderate
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of KT170 — Small signal
Transconductance	14 mA/V

Capacitances

Specifications of KT170 — Capacitances
Input	16.5 pF
Grid–plate	0.9 pF
Output	11.5 pF

Charactereditorial reading, not a measurement

Specifications of KT170 — 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 power (pp) stage

PA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 9, 2026Source : Tung-Sol KT170 spec PDF

Manufacturer datasheets

KT170 DatasheetFrank's Electron Tube Pages · PDF

SPICE models

Revision and verification status

Source: Tung-Sol KT170 spec PDF
Reviewed: 2026-05-09
Status: DataModelCalc
Model: under review

Context

The KT170 is a indirectly-heated beam tetrode from Tung-Sol, introduced around 2020. Commonly used in power (pp) applications. Largest KT. Massive headroom.

History

Introduced: 2020
Manufacturer: Tung-Sol
Era: Modern

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