What is the GMI-6 vacuum tube?

The GMI-6 (GMI-6 / ГМИ-6) is a tetrode vacuum tube designed for pulse modulator applications. Double beam tetrode. Pulse radar tube..

What is a GMI-6 substitute or equivalent?

Direct equivalents to the GMI-6 include No direct equivalent (Russian high-power transmitter beam tetrode). 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 GMI-6?

Max plate voltage 4000 V, max plate dissipation 15 W, heater 12.6 V / 1.1 A.

Is the GMI-6 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the GMI-6 as Rare 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 GMI-6 sound like?

Double beam tetrode. Pulse radar tube.. 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.

GMI-6 ГМИ-6 Tetrode Vacuum Tube

Also known as No direct equivalent (Russian high-power transmitter beam tetrode)

Beam power tetrode rated at 15W for high-power output stages

Dual tetrodeHeater 12.6 V · 1.1 ABaseless glass2 sectionsUlyanovsk 1958

Plate dissipation: 15W
Max plate voltage: 4000V

GMI-6

Characteristics

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

HeaterIndirectly heated

Specifications of GMI-6 — Heater
Heater voltageVh	12.6 V
Heater currentIh	1.1 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of GMI-6 — Limiting values
Plate voltageVa max	4000 V
Plate dissipationPa max	15 W

Mechanical

Specifications of GMI-6 — Mechanical
Base	Baseless glass
Rarity	Rare
Pinout

Capacitances

Specifications of GMI-6 — Capacitances
Input	14.5 pF
Grid–plate	0.2 pF
Output	5.2 pF

Charactereditorial reading, not a measurement

Specifications of GMI-6 — Character
Gain	0%
Power	38%
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
Phase splitter

Generic tetrode pulse modulator stage

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : Soviet-Tubes GMI-6 · pulse rating: 4kV pulse / 1kV CW

Manufacturer datasheets

1 manufacturer datasheets cross-checked for GMI-6 / ГМИ-61 verified

GMI-6 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Soviet-Tubes GMI-6 · pulse rating: 4kV pulse / 1kV CW
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

The GMI-6 is a dual indirectly-heated beam tetrode from Ulyanovsk, introduced around 1958. Commonly used in pulse modulator applications. Double beam tetrode. Pulse radar tube.

History

Introduced: 1958
Manufacturer: Ulyanovsk
Era: Golden Age

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