What is the 6528 vacuum tube?

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

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.

6528 Triode Vacuum Tube

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

TriodeHeater 6.3 V · 5 AOctalTung-Sol 1960

Plate dissipation: 30W
Max plate voltage: 400V
Transconductance: 37mA/V

6528

Characteristics

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

HeaterIndirectly heated

Specifications of 6528 — Heater
Heater voltageVh	6.3 V
Heater currentIh	5 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6528 — Limiting values
Plate voltageVa max	400 V
Plate dissipationPa max	30 W

Mechanical

Specifications of 6528 — Mechanical
Base	Octal
Rarity	Sought-after
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6528 — Small signal
Transconductance	37 mA/V
Plate resistance	245 Ω
Amplification factor	9

Capacitances

Specifications of 6528 — Capacitances
Grid–cathode	17.8 pF
Grid–plate	23.8 pF
Plate–cathode	2.9 pF

Charactereditorial reading, not a measurement

Specifications of 6528 — Character
Gain	9%
Power	75%
Drive	100%
Linearity	95%

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

SET output
Push-pull output
Headphone output

Generic triode otl stage

Headphone ampPA/public address

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : audit-us_a (CLEAN — matches canonical datasheet)

Manufacturer datasheets

3 manufacturer datasheets cross-checked for 65283 verified

6528 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: audit-us_a (CLEAN — matches canonical datasheet)
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

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.

History

Introduced: 1960
Manufacturer: Tung-Sol
Era: Late Production

METRIX TESTER