What is the 211 vacuum tube?

The 211 (211 / VT-4C) is a triode vacuum tube designed for transmitting (set) applications. Transmitting triode. Mighty bass..

What is a 211 substitute or equivalent?

Direct equivalents to the 211 include VT-4C, 242C. 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 211?

Amplification factor μ ≈ 12, transconductance gm ≈ 3.3 mA/V, plate resistance rp ≈ 3.6 kΩ, max plate voltage 1250 V, max plate dissipation 100 W, heater 10 V / 3.25 A.

Is the 211 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 211 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 211 sound like?

Transmitting triode. Mighty bass.. 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.

211 VT-4C Triode Vacuum Tube

Also known as VT-4C

Power triode delivering 100W for push-pull and SET designs

TriodeHeater 10 V · 3.25 AUX-4GE·RCA 1929

Plate dissipation: 100W
Max plate voltage: 1250V
Transconductance: 3.3mA/V

211

Characteristics

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

HeaterDirectly heated

Specifications of 211 — Heater
Heater voltageVh	10 V
Heater currentIh	3.25 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 211 — Limiting values
Plate voltageVa max	1250 V
Plate dissipationPa max	100 W

Mechanical

Specifications of 211 — Mechanical
Base	UX-4
Rarity	Moderate
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 211 — Small signal
Transconductance	3.3 mA/V
Plate resistance	3.6 kΩ
Amplification factor	12

Capacitances

Specifications of 211 — Capacitances
Grid–cathode	5.4 pF
Grid–plate	14 pF
Plate–cathode	4.8 pF

Charactereditorial reading, not a measurement

Specifications of 211 — Character
Gain	12%
Power	100%
Drive	96%
Linearity	94%

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	Load	Pout	gm	rp	Source
Class A, single-endedtriode connection · fixed bias	750 V	-46 V	34 mA	8.8 kΩ	5.6 W	2.75 mA/V	4.4 kΩ	OCR, to be checked RCA · p. 1 · transcript
triode connection, push-pullclass not stated · fixed bias	1000 V	-77 V	130 mA		40 W			OCR, to be checked RCA · p. 2 · transcript

SPICE model2 available

Model at this condition: Ayumi Nakabayashi · 2 engines Model
μ: 11.8
gm: 2.78 mA/V
rp: 4.2 kΩ

Design a stage →

Using this tube

Applications

SET output
Push-pull output

Audio Note OngakuCary CAD-805

PA/public address

Classic circuits

211 SE Classic
Single-Ended Triode16W
VT-4C/211 transmitting triode in audio service. High-voltage SE with commanding dynamics and visceral impact. Thunderous bass authority.
SEVb 750V · Vg -72V · RL 10kΩGE 211/VT-4C Datasheet

Replace or compare

Sources

By Jean-Michel Falligan DevergneReviewed May 29, 2026Source : GE·RCA datasheet · cap audit 2026-05-09Active model : Ayumi Nakabayashi · 2 engines

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 211 / VT-4C2 verified

211 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

Source: GE·RCA datasheet · cap audit 2026-05-09
Reviewed: 2026-05-29
Status: DataModelCalc
Model: Ayumi Nakabayashi · 2 engines

Context

The 211 (VT-4C) is a directly-heated thoriated-tungsten power triode originally developed for military radio transmitter service. Running at plate voltages of 800-1250V, it can deliver 15-25W in single-ended Class A with a fast, dynamic, and slightly forward presentation compared to the warmer 300B. The thoriated-tungsten filament runs at bright incandescence and gives the tube exceptional transient speed and high-frequency extension. GE and RCA NOS examples are the standard, with current production from Shuguang and Psvane offering more affordable alternatives.

History

Introduced: 1929
Manufacturer: GE·RCA
Era: Pre-War

METRIX TESTER

Characteristics

HeaterDirectly heated

Limiting valuesDatasheet maximum ratings — not to be exceeded

Mechanical

Small signalDatasheet parameters at the reference operating point — not limits

Capacitances

Charactereditorial reading, not a measurement?

Typical operation

Using this tube

Applications

Classic circuits

211 SE Classic

Replace or compare

Direct equivalents

Variants

Versus 01A

Comparisons

Similar tubes