What is the CV591 vacuum tube?

The CV591 is a pentode vacuum tube designed for preamp applications. Military 6SJ7..

What is a CV591 substitute or equivalent?

Direct equivalents to the CV591 include 6SJ7 mil. 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 CV591?

Transconductance gm ≈ 1.65 mA/V, max plate voltage 300 V, max plate dissipation 2.5 W, heater 6.3 V / 0.3 A.

Is the CV591 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the CV591 as Moderate 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 CV591 sound like?

Military 6SJ7.. 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 9, 2026

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CV591 Pentode Vacuum Tube

Pentode6.3V / 0.3AOctalSPICE

Sourceaudit-eu_a (CLEAN — matches canonical datasheet)Reviewed2026-05-09StatusDataModelCalcModelKoren pentodePDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗SPICE

CV591 — Mullard — pentode vacuum tube — (1942)

1.6mA/V

5.0pF

0.0pF

4.00pF

GAIN0%

POWER6%

DRIVE50%

LINEARITY75%

SPECIFICATIONS

Heater6.3 V · 0.3 A

Max Plate Voltage300 V

Pa max2.5 W

Gain Factor—

gm1.65 mA/V

rp—

Inter-electrode capacitances

Cgk5 pF

Cgp0.01 pF

Cpk4 pF

PinoutOctal

Era1942

RarityModerate

HEATER6.3V / 0.3A

MAX PLATE300V / 2.5W

BASEoctal

EXECUTIVE SUMMARY

The CV591 is a indirectly-heated pentode from Mullard, introduced around 1942. Commonly used in preamp applications. Military 6SJ7.

APPLICATIONS

Voltage amplifier

Generic pentode preamp stage

HISTORY

Introduced1942ManufacturerMullard

Pre-War

CV591 Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

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