What is a 6FD7 substitute or equivalent?

Direct equivalents to the 6FD7 include 13FD7. 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 6FD7?

Max plate voltage 330 V, max plate dissipation 10 W, heater 6.3 V / 0.925 A.

Is the 6FD7 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6FD7 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 6FD7 sound like?

Asymmetric dual: high-μ driver + low-μ output. Sister of 6EM7/6CY7 with slightly different ratings.. 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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6FD7 Triode Vacuum Tube

Q: What is the 6FD7 vacuum tube?

The 6FD7 is a triode vacuum tube designed for driver + power applications. Asymmetric dual: high-μ driver + low-μ output. Sister of 6EM7/6CY7 with slightly different ratings..

Dual triode6.3V / 0.925A9-pin Noval

SourceRCA 6FD7 datasheetReviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Power triode delivering 10W for push-pull and SET designs

Datasheet ↗

6FD7 — Sylvania·RCA — triode vacuum tube — (1960)

Asymmetric sections — each unit has its own characteristics

Unit 1 — High-μ (driver)

40.0kΩ

1.6mA/V

Pd max2.5W

2.2pF

4.5pF

0.40pF

Unit 2 — Low-μ (output)

800Ω

7.5mA/V

Pd max7.5W

6.5pF

10.0pF

1.20pF

SPECIFICATIONS

Heater6.3 V · 0.925 A

Max Plate Voltage330 V

Pa max10 W

Gain Factor—

gm—

rp—

Inter-electrode capacitances

Cgk2.2 pF

Cgp4.5 pF

Cpk0.4 pF

Pinout9-pin Noval

Era1960

RarityModerate

HEATER6.3V / 0.925A

MAX PLATE330V / 10W

BASEnoval

SECTIONS2 (dual)

Source datasheets

2 manufacturer datasheets cross-checked for 6FD7

2 verified

EXECUTIVE SUMMARY

The 6FD7 is a dual indirectly-heated triode from Sylvania·RCA, introduced around 1960. Commonly used in driver + power applications. Asymmetric dual: high-μ driver + low-μ output. Sister of 6EM7/6CY7 with slightly different ratings.

APPLICATIONS

SET outputPush-pull outputPhase splitter

Generic triode driver + power stage

• Hi-Fi stereo

HISTORY

Introduced1960ManufacturerSylvania·RCA

Late Production

6FD7 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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