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.

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..

Also known as 13FD7

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

Dual triodeHeater 6.3 V · 0.925 A9-pin Noval2 sectionsSylvania·RCA 1960

Plate dissipation: 10W
Max plate voltage: 330V

6FD7

Characteristics

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

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

HeaterIndirectly heated

Specifications of 6FD7 — Heater
Heater voltageVh	6.3 V
Heater currentIh	0.925 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6FD7 — Limiting values
Plate voltageVa max	330 V
Plate dissipationPa max	10 W

Mechanical

Specifications of 6FD7 — Mechanical
Base	9-pin Noval
Rarity	Moderate
Pinout

datasheet cited · model or editorial reading · catalogue value, no citation attached yet · nothing invented

Typical operation

Conditions published by the manufacturers, one row per condition. Nothing is computed.

Typical operation
Setup	Va	Vg1 / Rk	Ia	μ	rp	Source
Class A, single-endedtriode connection · fixed bias	250 V	-3 V	1.4 mA	64	40 kΩ	OCR, to be checked RCA · 1962 · p. 1 · transcript

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
Phase splitter

Generic triode driver + power stage

Hi-Fi stereo

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : RCA 6FD7 datasheet

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 6FD72 verified

6FD7 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: RCA 6FD7 datasheet
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

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.

History

Introduced: 1960
Manufacturer: Sylvania·RCA
Era: Late Production

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