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Tube Database (7,341 tube types · 1,270 archive entries)

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Tube-number record

HL25

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BrandFerranti
ClassHigh Voltage Control Triode
BaseOctal
Filament4 V @ 1000 mA

Construction

Primary TypeTriode
EnvelopeSilicone coated clear glass
Sections1

Filament / Heater

Heater NotesIndirectly heated

Absolute Maximum Ratings

Plate Voltage15000 V
Plate Dissipation4 W
Grid 1 Voltage-150 V
Cathode Current1 mA
H-C Voltage150 V

Audio Performance

Key Features
  • Silicone coated clear glass
  • High voltage control valve
  • Voltage regulator application

Typical Operation

ModePlate VGm (µmhos)Rp (Ω)µPlate mA
Cut-off15000 V————
la = 5uA15000 V———0.005 mA

Application Notes

The high voltages normally applied to this valve can be very dangerous. Particular care should be taken when making circuit adjustments.

Filters

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