What is the 6U8A-P vacuum tube?

The 6U8A-P (6U8A (Pentode)) is a pentode vacuum tube designed for preamp applications. Pentode section..

What is a 6U8A-P substitute or equivalent?

Direct equivalents to the 6U8A-P include ECF82. 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 6U8A-P?

Transconductance gm ≈ 5 mA/V, plate resistance rp ≈ 200.0 kΩ, max plate voltage 330 V, max plate dissipation 3 W, heater 6.3 V / 0.45 A.

Is the 6U8A-P still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6U8A-P as Common 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 6U8A-P sound like?

Pentode section.. 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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6U8A-P 6U8A (Pentode) Pentode Vacuum Tube

Pentode6.3V / 0.45A9-pin NovalSPICE

Sourceaudit-us_b (CLEAN — matches canonical datasheet)Reviewed2026-05-29StatusDataModelCalcModelKoren pentodePDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗SPICE

6U8A (Pentode) — RCA — pentode vacuum tube — (1955)

200.0kΩ

5.0mA/V

5.0pF

0.0pF

2.60pF

GAIN0%

POWER8%

DRIVE0%

LINEARITY75%

SPECIFICATIONS

Heater6.3 V · 0.45 A

Max Plate Voltage330 V

Pa max3 W

Gain Factor—

gm5 mA/V

rp200.0 kΩ

Inter-electrode capacitances

Cgk5 pF

Cgp0.015 pF

Cpk2.6 pF

Pinout9-pin Noval

Era1955

RarityCommon

HEATER6.3V / 0.45A

MAX PLATE330V / 3W

BASEnoval

Source datasheets

3 manufacturer datasheets cross-checked for 6U8A (Pentode)

3 verified

EXECUTIVE SUMMARY

The 6U8A-P is a indirectly-heated pentode from RCA, introduced around 1955. Commonly used in preamp applications. Pentode section.

APPLICATIONS

Voltage amplifier

Generic pentode preamp stage

HISTORY

Introduced1955ManufacturerRCA

Golden Age

6U8A-P Datasheet

Local mirror · PDF

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METRIX TESTER

Test this tube on a Metrix

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