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Voltage Pentode or Tetrode (under 100V) ·Pentode

DF66

Mullard subminiature AF voltage-amplifying pentode for hearing aids and low-current battery service. Its directly heated construction provides small-signal audio gain while keeping filament consumption suitable for miniature portable equipment.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
SUBMINIATURE
Socket code
WIRE8
Base pins
8
Nominal heater
0.625 V / 15 mA

Description

The Mullard DF66 is a subminiature AF voltage-amplifying pentode for hearing aids and low-current battery service.

Socket description

Subminiature all-glass 8-wire lead family

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
SUBMINIATURE
Socket code
WIRE8
Base pins
8
Nominal heater voltage
0.625 V
Nominal heater current
15 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

SUBMINIATURE - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Pentode

X-ray radiationInterelectrode capacitances
Plate resistance
2000000 Ω
Transconductance
0.0001 S
Max plate voltage
45 V
Max screen voltage
45 V

Subminiature AF pentode for hearing-aid service.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1951 Mullard Valve and Service Manual

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristics

  • Anode Voltage

    22.5 V

  • Screen Voltage

    22.5 V

  • Anode Current

    50 uA

Data set 02

1963 Mullard

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristics

  • Filament Voltage

    0.625 V

  • Filament Current

    15 mA

  • Plate Voltage

    22.5 V

  • Screen Voltage

    22.5 V

  • Plate Current

    0.05 mA

  • Screen Current

    0.015 mA

  • Grid Voltage

    -1.05 V

  • Transconductance

    100 uS

  • Plate Resistance

    2000000 ohm

    Minimum

Other

  • Voltage Gain

    33 ratio

    ResistanceCoupled; FixedBias

  • Voltage Gain

    35 ratio

    ResistanceCoupled; GridCurrentBias

  • Maximum Plate Voltage

    45 V

  • Maximum Screen Voltage

    45 V

  • Maximum Cathode Current

    0.1 mA

Data set 03

1963 Philips Electron Tubes Handbook V1

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

  • Control-grid capacitance

    1.6 pF

  • Plate capacitance

    2.2 pF

  • Grid-to-plate capacitance

    0.15 pF

Other

  • Plate voltage

    22.5 V

    HearingAid

  • Screen voltage

    22.5 V

    HearingAid

  • Plate current

    50 uA

    HearingAid

  • Screen current

    15 uA

    HearingAid

  • Grid voltage

    -1.05 V

    HearingAid

Characteristic

  • Transconductance

    100 uS

Data set 04

1999 Philips 0-D

Published operating points and test conditions from this source.

SECTION 1

Pentode

Capacitance

  • Input capacitance

    1.6 pF

  • Output capacitance

    2.2 pF

  • Plate-grid capacitance maximum

    0.15 pF

Characteristics

  • Plate voltage

    22.5 V

  • Screen voltage

    22.5 V

  • Plate current

    50 uA

  • Screen current

    15 uA

  • Grid bias

    -1.05 V

  • Transconductance

    100 uS

  • Plate resistance

    2 Mohm

    Minimum

  • Screen-grid amplification factor

    11.5