What is the 10Y vacuum tube?

The 10Y (10Y / VT-25) is a triode vacuum tube designed for power (set) applications. Legendary DHT. Ethereal midrange clarity..

What is a 10Y substitute or equivalent?

Direct equivalents to the 10Y include VT-25, UX-210, 801A. 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 10Y?

Amplification factor μ ≈ 8, transconductance gm ≈ 1.5 mA/V, plate resistance rp ≈ 5.3 kΩ, max plate voltage 450 V, max plate dissipation 15 W, heater 7.5 V / 1.25 A.

Is the 10Y still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 10Y 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 10Y sound like?

Legendary DHT. Ethereal midrange clarity.. 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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10Y 10Y / VT-25 Triode Vacuum Tube

Triode7.5V / 1.25AUX-4

SourceRCA·GE·SylvaniaReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Power triode delivering 15W for push-pull and SET designs

Datasheet ↗

10Y / VT-25 — RCA·GE·Sylvania — triode vacuum tube — (1927)

5.3kΩ

1.5mA/V

4.0pF

7.0pF

3.00pF

GAIN8%

POWER38%

DRIVE95%

LINEARITY95%

SPECIFICATIONS

Heater7.5 V · 1.25 A

Max Plate Voltage450 V

Pa max15 W

Gain Factor8

gm1.5 mA/V

rp5.3 kΩ

Inter-electrode capacitances

Cgk4 pF

Cgp7 pF

Cpk3 pF

PinoutUX-4

Era1927

RarityCollector

HEATER7.5V / 1.25A

MAX PLATE450V / 15W

BASEux4

Source datasheets

1 manufacturer datasheets cross-checked for 10Y / VT-25

1 verified

EXECUTIVE SUMMARY

The 10Y is a directly-heated triode from RCA·GE·Sylvania, introduced around 1927. It provides a gain factor (μ) of 8 with 5300Ω plate resistance. Commonly used in power (set) applications. Legendary DHT. Ethereal midrange clarity.

APPLICATIONS

SET outputPush-pull output

Generic triode power (set) stage

• Hi-Fi stereo

HISTORY

Introduced1927ManufacturerRCA·GE·Sylvania

Pre-War

10Y 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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