What is the VT-103 vacuum tube?

The VT-103 is a tetrode vacuum tube designed for preamp applications. Military designation..

What is a VT-103 substitute or equivalent?

Direct equivalents to the VT-103 include 6SQ7. 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 VT-103?

Amplification factor μ ≈ 100, transconductance gm ≈ 6 mA/V, plate resistance rp ≈ 91.0 kΩ, max plate voltage 750 V, max plate dissipation 30 W, heater 6.3 V / 0.3 A.

Is the VT-103 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the VT-103 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 VT-103 sound like?

Military designation.. 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.

VT-103 Tetrode Vacuum Tube

Also known as 6SQ7

Beam power tetrode rated at 30W for high-power output stages

TetrodeHeater 6.3 V · 0.3 AOctalRCA 1942

Plate dissipation: 30W
Max plate voltage: 750V
Transconductance: 6mA/V

VT-103

Characteristics

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

HeaterIndirectly heated

Specifications of VT-103 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.3 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of VT-103 — Limiting values
Plate voltageVa max	750 V
Plate dissipationPa max	30 W

Mechanical

Specifications of VT-103 — Mechanical
Base	Octal
Rarity	Rare
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of VT-103 — Small signal
Transconductance	6 mA/V
Plate resistance	91 kΩ
Amplification factor	100

Capacitances

Specifications of VT-103 — Capacitances
Input	11 pF
Grid–plate	0.2 pF
Output	7 pF

Charactereditorial reading, not a measurement

Specifications of VT-103 — Character
Gain	100%
Power	75%
Drive	9%
Linearity	50%

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

Using this tube

Applications

High-power output

Generic tetrode preamp stage

PA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : amplifiedparts 6SQ7 (= VT-103)Active model : Norman Koren

Manufacturer datasheets

2 manufacturer datasheets cross-checked for VT-1032 verified

VT-103 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: amplifiedparts 6SQ7 (= VT-103)
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Norman Koren

Context

The VT-103 is a indirectly-heated beam tetrode from RCA, introduced around 1942. It provides a gain factor (μ) of 100 with 91.0kΩ plate resistance. Commonly used in preamp applications. Military designation.

History

Introduced: 1942
Manufacturer: RCA
Era: Pre-War

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