What is the 2A3 vacuum tube?

The 2A3 is a triode vacuum tube designed for power (set) applications. Crystalline SE power..

What is a 2A3 substitute or equivalent?

Direct equivalents to the 2A3 include None standard. 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 2A3?

Amplification factor μ ≈ 4, transconductance gm ≈ 5.25 mA/V, plate resistance rp ≈ 800 Ω, max plate voltage 300 V, max plate dissipation 15 W, heater 2.5 V / 2.5 A.

Is the 2A3 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 2A3 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 2A3 sound like?

Crystalline SE power.. 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

←2A3

← 274B 2A3-40 JJ →Compare…

2A3 Triode Vacuum Tube

Triode2.5V / 2.5AUX-4SPICE

SourceRCA·WE·Shuguang datasheetReviewed2026-05-29StatusDataModelCalcModelKoren v1PDF

High-power directly-heated triode for single-ended amplification

Datasheet ↗SPICE

2A3 — RCA·WE·Shuguang — triode vacuum tube — (1932)

800Ω

5.3mA/V

7.5pF

16.5pF

5.50pF

GAIN4%

POWER38%

DRIVE99%

LINEARITY95%

SPECIFICATIONS

Heater2.5 V · 2.5 A

Max Plate Voltage300 V

Pa max15 W

Gain Factor4

gm5.25 mA/V

rp800 Ω

Inter-electrode capacitances

Cgk7.5 pF

Cgp16.5 pF

Cpk5.5 pF

PinoutUX-4

Era1932

RarityCollector

HEATER2.5V / 2.5A

MAX PLATE300V / 15W

BASEux4

Source datasheets

4 manufacturer datasheets cross-checked for 2A3

4 verified

TYPICAL OPERATING POINT

SPICE model(2 available)5 .subckt available ↓

Va300V

Ia32.43mA

Vg-62.557V

Pd9.73W

RL3kΩ

Av9dB

EXECUTIVE SUMMARY

The 2A3 is a directly-heated power triode introduced by RCA in 1930, delivering about 3.5W in single-ended Class A. It has a remarkably low plate resistance (~800 ohms) for a DHT, giving it excellent damping factor and tight bass response without feedback. The 2A3 occupies a sweet spot between the delicacy of the 45 and the authority of the 300B, with a midrange that many consider the most natural of any power tube. Single-plate versions (such as the RCA mono-plate and Sovtek 2A3) are generally preferred over the original dual-plate construction for lower distortion and better linearity.

APPLICATIONS

SET outputPush-pull outputHeadphone output

Western Electric 86 amplifierCary CAD-2A3SE

• Hi-Fi stereo• Headphone amp

HISTORY

Introduced1932ManufacturerRCA·WE·Shuguang

Pre-War

2A3 Datasheet

Local mirror · PDF

↗

METRIX TESTER

Test this tube on a Metrix

CLASSIC CIRCUITS

Hi-Fi Classic

Audio Note Kit 1 / Ongaku Style

3.5W

Single-ended 2A3 in the Audio Note tradition. Direct-heated triode purity with simple signal path. Intimate, holographic sound.

SEVb 250V · Vg -45V · RL 2.5kΩ

Audio Note Kit 1 Design

Single-Ended Triode

2A3 SE Classic

3.5W

Standard single-ended 2A3 operating point per RCA data. Direct-heated triode at its most pure. Sweet, intimate, and harmonically rich.

SEVb 250V · Vg -45V · RL 2.5kΩ

RCA 2A3 Datasheet

Single-Ended Triode

6B4G SE Classic

3.5W

Octal-base equivalent of the 2A3. Same operating parameters with a more modern base. Practical alternative for SE triode designs.

SEVb 250V · Vg -45V · RL 2.5kΩ

RCA 6B4G Datasheet

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