What is the 6900 vacuum tube?

The 6900 is a triode vacuum tube designed for driver / preamp applications. Bendix premium. Military-spec 5687. Holy grail..

What is a 6900 substitute or equivalent?

Direct equivalents to the 6900 include 5687, 7044. 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 6900?

Amplification factor μ ≈ 18, transconductance gm ≈ 11.5 mA/V, plate resistance rp ≈ 1.7 kΩ, max plate voltage 600 V, max plate dissipation 4.25 W, heater 12.6 V / 0.45 A.

Is the 6900 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 6900 as Collector 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 6900 sound like?

Bendix premium. Military-spec 5687. Holy grail.. 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.

6900 Triode Vacuum Tube

Also known as 5687 · 7044

Medium-gain triode for driver and line stage applications

Dual triodeHeater 12.6 V · 0.45 A9-pin Noval2 sectionsBendix 1960

Plate dissipation: 4.25W
Max plate voltage: 600V
Amplification factor: 18
Transconductance: 11.5mA/V
Plate resistance: 1.7kΩ

6900

Characteristics

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

HeaterIndirectly heated

Specifications of 6900 — Heater
Heater voltageVh	12.6 V
Heater currentIh	0.45 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 6900 — Limiting values
Plate voltageVa max	600 V
Plate dissipationPa max	4.25 W

Mechanical

Specifications of 6900 — Mechanical
Base	9-pin Noval
Rarity	Collector
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 6900 — Small signal
Transconductance	11.5 mA/V
Plate resistance	1.7 kΩ
Amplification factor	18

Capacitances

Specifications of 6900 — Capacitances
Grid–cathode	6.5 pF
Grid–plate	4 pF
Plate–cathode	0.8 pF

Charactereditorial reading, not a measurement

Specifications of 6900 — Character
Gain	18%
Power	11%
Drive	98%
Linearity	91%

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

Voltage amplifier
Headphone output
Line stage
Phase splitter

Generic triode driver / preamp stage

Hi-Fi stereoHeadphone amp

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 69002 verified

6900 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: Bendix
Reviewed: 2026-05-29
Status: DataModelCalc
Model: under review

Context

The 6900 is a dual indirectly-heated triode from Bendix, introduced around 1960. It provides a gain factor (μ) of 18 with 1700Ω plate resistance. Commonly used in driver / preamp applications. Bendix premium. Military-spec 5687. Holy grail.

History

Introduced: 1960
Manufacturer: Bendix
Era: Late Production

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