What is the C3g vacuum tube?

The C3g is a pentode vacuum tube designed for preamp / driver applications. German Post legend. Ultra-linear..

What is a C3g substitute or equivalent?

Direct equivalents to the C3g include C3m. 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 C3g?

Amplification factor μ ≈ 41, transconductance gm ≈ 14 mA/V, plate resistance rp ≈ 300.0 kΩ, max plate voltage 220 V, max plate dissipation 3.5 W, heater 6.3 V / 0.37 A.

Is the C3g still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the C3g 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 C3g sound like?

German Post legend. Ultra-linear.. 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

←C3g

← AZ4 C3m →Compare → C3m

C3g Pentode Vacuum Tube

Pentode6.3V / 0.37A8-pin Loctal

SourceSiemens C3g datasheet (vacuumtubes.io)Reviewed2026-05-29StatusDataModelCalcModelunder reviewPDF

Small-signal pentode for low-noise voltage amplification

Datasheet ↗

C3g — Siemens — pentode vacuum tube — (1954)

300.0kΩ

14.0mA/V

9.5pF

0.0pF

3.50pF

GAIN41%

POWER9%

DRIVE0%

LINEARITY80%

SPECIFICATIONS

Heater6.3 V · 0.37 A

Max Plate Voltage220 V

Pa max3.5 W

Gain Factor41

gm14 mA/V

rp300.0 kΩ

Inter-electrode capacitances

Cgk9.5 pF

Cgp0.012 pF

Cpk3.5 pF

Pinout8-pin Loctal

Era1954

RaritySought-after

HEATER6.3V / 0.37A

MAX PLATE220V / 3.5W

BASEspecial-8

Source datasheets

3 manufacturer datasheets cross-checked for C3g

3 verified

Triode-connectedTelefunken010163 / 020163 / 030163 / 040163 (1963) — "Vorlaeufige technische Daten / Tentative data"

Specs when the screen grid (g2) is tied to the anode — the tube acts as a triode.

17 mA

17 mA/V

200

According to Telefunken (010163 / 020163 / 030163 / 040163 (1963) — "Vorlaeufige technische Daten / Tentative data"): « g2 an a »

EXECUTIVE SUMMARY

The C3g is a indirectly-heated pentode from Siemens, introduced around 1954. It provides a gain factor (μ) of 41 with 300.0kΩ plate resistance. Commonly used in preamp / driver applications. German Post legend. Ultra-linear.

APPLICATIONS

Voltage amplifier

Generic pentode preamp / driver stage

VS C3m

μ +116%Rp +20%Pd -12%Full comparison →

HISTORY

Introduced1954ManufacturerSiemens

Golden Age

C3g 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.

SIMILAR PENTODES

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