What is the 5998 vacuum tube?

The 5998 is a triode vacuum tube designed for power/output applications. OTL king. Muscular current delivery..

What is a 5998 substitute or equivalent?

Direct equivalents to the 5998 include 421A, 7236. 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 5998?

Amplification factor μ ≈ 6, transconductance gm ≈ 14 mA/V, plate resistance rp ≈ 350 Ω, max plate voltage 275 V, max plate dissipation 15 W, heater 6.3 V / 2.4 A.

Is the 5998 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 5998 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 5998 sound like?

OTL king. Muscular current delivery.. 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

←5998

← 5977 5AQ5 →Compare → 421A

5998 Triode Vacuum Tube

Dual triode6.3V / 2.4AOctalSPICE

SourceTung-SolReviewed2026-05-29StatusDataModelCalcModel2 enginesPDF

Power triode delivering 15W for push-pull and SET designs

Datasheet ↗SPICE

5998 — Tung-Sol — triode vacuum tube — (1953)

350Ω

14.0mA/V

7.7pF

18.3pF

2.50pF

GAIN6%

POWER38%

DRIVE100%

LINEARITY95%

SPECIFICATIONS

Heater6.3 V · 2.4 A

Max Plate Voltage275 V

Pa max15 W

Gain Factor6

gm14 mA/V

rp350 Ω

Inter-electrode capacitances

Cgk7.7 pF

Cgp18.3 pF

Cpk2.5 pF

PinoutOctal

Era1953

RaritySought-after

HEATER6.3V / 2.4A

MAX PLATE275V / 15W

BASEoctal

SECTIONS2 (dual)

Source datasheets

1 manufacturer datasheets cross-checked for 5998

1 verified

TYPICAL OPERATING POINT

SPICE model(2 available)2 .subckt available ↓

Va120V

Ia45.22mA

Vg-15V

Pd5.43W

RL700Ω

Av9.4dB

EXECUTIVE SUMMARY

The 5998 is a dual indirectly-heated triode from Tung-Sol, introduced around 1953. It provides a gain factor (μ) of 6 with 350Ω plate resistance. Commonly used in power/output applications. OTL king. Muscular current delivery.

APPLICATIONS

SET outputPush-pull outputHeadphone outputPhase splitter

Generic triode power/output stage

• Hi-Fi stereo• Headphone amp

VS 421A

μ 0%Rp +0%Pd 0%Full comparison →

HISTORY

Introduced1953ManufacturerTung-Sol

Golden Age

5998 Datasheet

Local mirror · PDF

↗

METRIX TESTER

Test this tube on a Metrix

SIMILAR TRIODES

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