What is the TT22 vacuum tube?

The TT22 is a tetrode vacuum tube designed for power (pp) applications. 12V heater KT88 variant. RF/Audio crossover..

What is a TT22 substitute or equivalent?

Direct equivalents to the TT22 include KT88 (different pinout, 12V heater). 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 TT22?

Transconductance gm ≈ 11.5 mA/V, max plate voltage 1250 V, max plate dissipation 45 W, heater 12.6 V / 0.8 A.

Is the TT22 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the TT22 as Collector 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 TT22 sound like?

12V heater KT88 variant. RF/Audio crossover.. 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.

TT22 Tetrode Vacuum Tube

Also known as KT88 (different pinout · 12V heater)

Beam power tetrode rated at 45W for high-power output stages

TetrodeHeater 12.6 V · 0.8 AOctal + Top CapGEC·MOV 1957

Plate dissipation: 45W
Max plate voltage: 1250V
Transconductance: 11.5mA/V

TT22

Characteristics

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

HeaterIndirectly heated

Specifications of TT22 — Heater
Heater voltageVh	12.6 V
Heater currentIh	0.8 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of TT22 — Limiting values
Plate voltageVa max	1250 V
Plate dissipationPa max	45 W

Mechanical

Specifications of TT22 — Mechanical
Base	Octal + Top Cap
Rarity	Collector
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of TT22 — Small signal
Transconductance	11.5 mA/V

Capacitances

Specifications of TT22 — Capacitances
Input	12 pF
Grid–plate	0.5 pF
Output	8 pF

Charactereditorial reading, not a measurement

Specifications of TT22 — 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 : GEC TT22 datasheet (tubedatabase)

Manufacturer datasheets

TT22 DatasheetFrank's Electron Tube Pages · PDF

SPICE models

Revision and verification status

Source: GEC TT22 datasheet (tubedatabase)
Reviewed: 2026-05-09
Status: DataModelCalc
Model: under review

Context

The TT22 is a indirectly-heated beam tetrode from GEC·MOV, introduced around 1957. Commonly used in power (pp) applications. 12V heater KT88 variant. RF/Audio crossover.

History

Introduced: 1957
Manufacturer: GEC·MOV
Era: Golden Age

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