What is the 845 vacuum tube?

The 845 is a triode vacuum tube designed for transmitting (set) applications. King of SET output..

What is a 845 substitute or equivalent?

Direct equivalents to the 845 include VT-43. 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 845?

Amplification factor μ ≈ 5, transconductance gm ≈ 3.3 mA/V, plate resistance rp ≈ 1.7 kΩ, max plate voltage 1250 V, max plate dissipation 100 W, heater 10 V / 3.25 A.

Is the 845 still in production?

Production status varies by year and manufacturer. The current Amperatubes catalog classifies the 845 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 845 sound like?

King of SET output.. 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.

845 Triode Vacuum Tube

Also known as VT-43

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

TriodeHeater 10 V · 3.25 AUX-4RCA 1931

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

845

Characteristics

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

HeaterDirectly heated

Specifications of 845 — Heater
Heater voltageVh	10 V
Heater currentIh	3.25 A

Limiting valuesDatasheet maximum ratings — not to be exceeded

Specifications of 845 — Limiting values
Plate voltageVa max	1250 V
Plate dissipationPa max	100 W

Mechanical

Specifications of 845 — Mechanical
Base	UX-4
Rarity	Moderate
Pinout

Small signalDatasheet parameters at the reference operating point — not limits

Specifications of 845 — Small signal
Transconductance	3.3 mA/V
Plate resistance	1.7 kΩ
Amplification factor	5

Capacitances

Specifications of 845 — Capacitances
Grid–cathode	5 pF
Grid–plate	13.5 pF
Plate–cathode	3.5 pF

Charactereditorial reading, not a measurement

Specifications of 845 — Character
Gain	5%
Power	100%
Drive	98%
Linearity	95%

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

Using this tube

Applications

SET output
Push-pull output
Headphone output

Cary CAD-805Mastersound 845 integrated

Headphone ampPA/public address

Classic circuits

845 SE Classic
Single-Ended Triode22W
RCA 845 transmitting triode in SE configuration. Even higher voltage than the 211 with a more linear transfer characteristic. Massive, effortless power.
SEVb 1000V · Vg -98V · RL 10kΩRCA 845 Datasheet

Replace or compare

Sources

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

Manufacturer datasheets

2 manufacturer datasheets cross-checked for 8452 verified

845 DatasheetLocal mirror · PDF

SPICE models

Revision and verification status

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

Context

The 845 is a transmitting triode closely related to the 211 but with a higher amplification factor (mu ~8 versus ~12 for the 211), originally made by RCA and Amperex. Operating at plate voltages of 800-1250V, it delivers 15-30W in single-ended Class A with a slightly warmer, fuller tonal balance than the 211. The 845's higher mu means it requires less drive voltage, simplifying the driver stage design somewhat. It shares the 211's dramatic visual presence with its bright thoriated-tungsten filament, and the two are often compared as complementary voices in the DHT transmitting triode world.

History

Introduced: 1931
Manufacturer: RCA
Era: Pre-War

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