421A
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BrandWestern Electric
ClassDouble Power Triode
BaseOctal
Filament6.3V @ 2500mA
Construction
Primary TypeDouble Triode
EnvelopeGlass
Sections2
Filament / Heater
Heater NotesIndirectly heated
Absolute Maximum Ratings
Plate Voltage250 V
Plate Dissipation13 W
Cathode Current125 mA
H-C Voltage300 V
Audio Performance
Power Output3.5 W
Key Features
- Low amplification factor
- High transconductance
- High plate current capability
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Class A1 (per section) | 135V | 7000 | 280 | 2 | 125mA |
Application Notes
Commonly used in voltage regulators and OTL audio amplifier output stages.
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