Tube-number record
348A
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348A is a tube type in the TubeDatabase archive (class: Suppressor-grid pentode). Recorded specifications: brand Western Electric, construction Pentode, base Small shell, socket Octal, and maximum plate voltage 250 V. The archive does not yet hold a photographed example of this type.
BrandWestern Electric
ClassSuppressor-grid pentode
BaseOctal
Filament6.3 V @ 500 mA
Construction
Primary TypePentode
EnvelopeBulb
Base MaterialSmall shell
Sectionssingle
Filament / Heater
Heater NotesIndirectly heated cathode; AC or DC operation.
Absolute Maximum Ratings
Plate Voltage250 V
Grid 2 Voltage180 V
Grid 1 Voltage-5.5 V
Audio Performance
Key Features
- Low tube noise
- Indirectly heated cathode
- Suppressor-grid pentode
- Audio-frequency voltage amplifier
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Recommended Conditions | 135 V | — | — | — | 5.5 mA |
| Recommended Conditions | 180 V | — | — | — | 5.5 mA |
| Maximum Conditions | 250 V | — | — | — | 5.6 mA |
| Maximum Conditions | 250 V | — | — | — | 6 mA |
Application Notes
The heater element is designed to operate on a voltage basis and it should be operated as near the rated voltage as practicable. Operation at a higher voltage will definitely reduce the life of the tube.
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