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.

By Jean-Michel Falligan Devergne · Reviewed May 29, 2026

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1625 1625 / VT-136 Tetrode Vacuum Tube

Tetrode12.6V / 0.45AOctal

SourceRCA·GEReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

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

Datasheet ↗

1625 / VT-136 — RCA·GE — tetrode vacuum tube — (1942)

6.0mA/V

11.0pF

0.2pF

7.00pF

GAIN8%

POWER75%

DRIVE50%

LINEARITY95%

SPECIFICATIONS

Heater12.6 V · 0.45 A

Max Plate Voltage750 V

Pa max30 W

Gain Factor8

gm6 mA/V

rp—

Inter-electrode capacitances

Cgk11 pF

Cgp0.2 pF

Cpk7 pF

PinoutOctal

Era1942

RarityCommon

HEATER12.6V / 0.45A

MAX PLATE750V / 30W

BASEoctal

Source datasheets

2 manufacturer datasheets cross-checked for 1625 / VT-136

2 verified

EXECUTIVE SUMMARY

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.

APPLICATIONS

High-power output

Generic tetrode transmitting / power stage

• PA/public address

HISTORY

Introduced1942ManufacturerRCA·GE

Pre-War

1625 Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

SPICE model not yet available. Loadline calculator requires calibrated Koren parameters.

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