What is the GZ34 vacuum tube?

The GZ34 (GZ34 / 5AR4) is a rectifier vacuum tube designed for rectifier applications. The premier audio rectifier..

What is a GZ34 substitute or equivalent?

Direct equivalents to the GZ34 include 5AR4, CV1377. 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.

Is the GZ34 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the GZ34 as Sought-after 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 GZ34 sound like?

The premier audio rectifier.. 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.

GZ34 5AR4 Rectifier Vacuum Tube

Also known as 5AR4 · CV1377

Full-wave rectifier for vacuum tube power supply designs

RectifierHeater 5 V · 1.9 AOctalMullard·Philips 1954

Max DC output current: 250mA
Peak inverse voltage: 1500V
Max RMS input per anode: 550V
Peak anode current: 750mA

GZ34

Characteristics

Datasheet values, once each. Every value cites its sheet.

HeaterDirectly heated

Specifications of GZ34 — Heater
Heater voltageVh	5 V
Heater currentIh	1.9 A

Rectifier limitsDatasheet maximum ratings — not to be exceeded

Specifications of GZ34 — Rectifier limits
Max RMS input voltage per anode	550 V
Io max (DC output current)	250 mA
Peak inverse voltage (PIV)	1500 V
Peak anode current	750 mA
Max reservoir capacitor	60 µF
Min series resistance per anode	175 Ω

Mechanical

Specifications of GZ34 — Mechanical
Base	Octal
Rarity	Sought-after
Pinout

datasheet cited · model or editorial reading · catalogue value, no citation attached yet · nothing invented

Using this tube

Interactive loadline calculator not available for this tube yet — it needs calibrated Koren or Ayumi parameters.

Applications

Power supply rectification

Marshall JTM45 PSUDynaco ST-70 PSU

Guitar amp

Featured in these amplifiers

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : Mullard·Philips datasheet

Manufacturer datasheets

5 manufacturer datasheets cross-checked for GZ34 / 5AR45 verified

GZ34 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Mullard·Philips datasheet
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

The GZ34 (5AR4) is a full-wave indirectly-heated rectifier developed by Mullard, capable of delivering up to 250mA with a relatively low voltage drop (~15V under full load). Its indirectly-heated cathode provides a slow, controlled warm-up that functions as a built-in soft-start for the power supply, gradually bringing B+ voltage up to operating level and extending the life of other tubes in the circuit. The GZ34's combination of high current capability and low voltage drop makes it the most capable of the common audio rectifiers. Mullard f32 and f33 coded fat-base versions from the Blackburn factory are the most prized, followed by Philips Heerlen and Amperex production.

History

Introduced: 1954
Manufacturer: Mullard·Philips
Era: Golden Age

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