What is the 71A vacuum tube?

The 71A is a triode vacuum tube designed for power (set) applications. Sub-watt SET. Intimate, delicate..

What is a 71A substitute or equivalent?

Direct equivalents to the 71A include 171A, VT-71A. 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 71A?

Amplification factor μ ≈ 3, transconductance gm ≈ 1.7 mA/V, plate resistance rp ≈ 1.8 kΩ, max plate voltage 180 V, max plate dissipation 4 W, heater 5 V / 0.25 A.

Is the 71A still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 71A 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 71A sound like?

Sub-watt SET. Intimate, delicate.. 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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71A Triode Vacuum Tube

Triode5V / 0.25AUX-4

SourceRCA·SylvaniaReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Low-mu triode with excellent linearity for driver and line stages

Datasheet ↗

71A — RCA·Sylvania — triode vacuum tube — (1926)

1.8kΩ

1.7mA/V

3.2pF

7.5pF

2.90pF

GAIN3%

POWER10%

DRIVE98%

LINEARITY95%

SPECIFICATIONS

Heater5 V · 0.25 A

Max Plate Voltage180 V

Pa max4 W

Gain Factor3

gm1.7 mA/V

rp1.8 kΩ

Inter-electrode capacitances

Cgk3.2 pF

Cgp7.5 pF

Cpk2.9 pF

PinoutUX-4

Era1926

RarityCollector

HEATER5V / 0.25A

MAX PLATE180V / 4W

BASEux4

Source datasheets

4 manufacturer datasheets cross-checked for 71A

4 verified

EXECUTIVE SUMMARY

The 71A is a directly-heated triode from RCA·Sylvania, introduced around 1926. It provides a gain factor (μ) of 3 with 1750Ω plate resistance. Commonly used in power (set) applications. Sub-watt SET. Intimate, delicate.

APPLICATIONS

Headphone outputLine stage

Generic triode power (set) stage

• Hi-Fi stereo• Headphone amp

HISTORY

Introduced1926ManufacturerRCA·Sylvania

Pre-War

71A 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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