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Power - Triode ·Triode

2A3MESH

Mesh-plate directly heated 2A3-family audio power triode. It retains the classic low-mu operating character while using distinctive mesh-anode construction, with published single-ended Class A service producing roughly 3.5 W into a 2.5 kΩ load.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
UX4
Socket code
UX4
Base pins
4
Nominal heater
2.5 V / 2.5 A

Description

Mesh-anode directly heated 2A3 replacement audio triode. The supplied Emission Labs sheet was read for filament data, maximum ratings, representative operating points, gm/rp/mu, output conditions, capacitances, and rectifier filter conditions as applicable.

Socket description

Medium-shell UX 4-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
UX4
Socket code
UX4
Base pins
4
Nominal heater voltage
2.5 V
Nominal heater current
2.5 A
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

UX4 - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Triode

X-ray radiationInterelectrode capacitances
Plate resistance
800 Ω
Transconductance
0.0052 S
Amplification factor
4.1
Max plate voltage
350 V
Max plate dissipation
18 W
Max cathode current
70 mA

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

2026 Emission Labs

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristics

  • Filament voltage

    2.5 V

  • Filament current

    2.5 A

  • Plate resistance

    800 ohm

    ClassA

  • Amplification factor

    4.1

    ClassA

  • Transconductance

    5200 uS

    ClassA

Other

  • Plate voltage

    250 V

    ClassA

  • Plate current

    60 mA

    ClassA

  • Grid voltage

    -45 V

    ClassA

  • Load resistance

    2500 ohm

    ClassA

  • Output power

    3.5 W

    ClassA