What is the 1625 vacuum tube?

The 1625 (1625 / VT-136) is a tetrode vacuum tube designed for transmitting / power applications. Military 807. 12.6V heater. WWII surplus..

What is a 1625 substitute or equivalent?

Direct equivalents to the 1625 include 807 (12.6V 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 1625?

Amplification factor μ ≈ 8, transconductance gm ≈ 6 mA/V, max plate voltage 750 V, max plate dissipation 30 W, heater 12.6 V / 0.45 A.

Is the 1625 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 1625 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 1625 sound like?

Military 807. 12.6V heater. WWII surplus.. 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.

1625 VT-136 Tetrode Vacuum Tube

Also known as 807 (12.6V heater)

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

TetrodeHeater 12.6 V · 0.45 AOctalRCA·GE 1942

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

1625

Characteristics

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

HeaterIndirectly heated

Specifications of 1625 — Heater
Heater voltageVh	12.6 V
Heater currentIh	0.45 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 1625 — Limiting values
Plate voltageVa max	750 V
Plate dissipationPa max	30 W

Mechanical

Specifications of 1625 — Mechanical
Base	Octal
Rarity	Common
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 1625 — Small signal
Transconductance	6 mA/V
Amplification factor	8

Capacitances

Specifications of 1625 — Capacitances
Input	11 pF
Grid–plate	0.2 pF
Output	7 pF

Charactereditorial reading, not a measurement

Specifications of 1625 — Character
Gain	8%
Power	75%
Drive	50%
Linearity	95%

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 transmitting / power stage

PA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 1625 / VT-1362 verified

1625 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: RCA·GE
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

The 1625 is a indirectly-heated beam tetrode from RCA·GE, introduced around 1942. Commonly used in transmitting / power applications. Military 807. 12.6V heater. WWII surplus.

History

Introduced: 1942
Manufacturer: RCA·GE
Era: Pre-War

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