What is the 6528 vacuum tube?

The 6528 is a triode vacuum tube designed for otl applications. High-current OTL output..

What is a 6528 substitute or equivalent?

Direct equivalents to the 6528 include None. 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 6528?

Amplification factor μ ≈ 9, transconductance gm ≈ 37 mA/V, plate resistance rp ≈ 245 Ω, max plate voltage 400 V, max plate dissipation 30 W, heater 6.3 V / 5 A.

Is the 6528 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6528 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 6528 sound like?

High-current OTL output.. 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

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6528 Triode Vacuum Tube

Triode6.3V / 5AOctal

Sourceaudit-us_a (CLEAN — matches canonical datasheet)Reviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Power triode delivering 30W for push-pull and SET designs

Datasheet ↗

6528 — Tung-Sol — triode vacuum tube — (1960)

245Ω

37.0mA/V

17.8pF

23.8pF

2.90pF

GAIN9%

POWER75%

DRIVE100%

LINEARITY95%

SPECIFICATIONS

Heater6.3 V · 5 A

Max Plate Voltage400 V

Pa max30 W

Gain Factor9

gm37 mA/V

rp245 Ω

Inter-electrode capacitances

Cgk17.8 pF

Cgp23.8 pF

Cpk2.9 pF

PinoutOctal

Era1960

RaritySought-after

HEATER6.3V / 5A

MAX PLATE400V / 30W

BASEoctal

Source datasheets

3 manufacturer datasheets cross-checked for 6528

3 verified

EXECUTIVE SUMMARY

The 6528 is a indirectly-heated triode from Tung-Sol, introduced around 1960. It provides a gain factor (μ) of 9 with 245Ω plate resistance. Commonly used in otl applications. High-current OTL output.

APPLICATIONS

SET outputPush-pull outputHeadphone output

Generic triode otl stage

• Headphone amp• PA/public address

HISTORY

Introduced1960ManufacturerTung-Sol

Late Production

6528 Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

SPICE model not yet available. Loadline calculator requires calibrated Koren parameters.

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