Voltage - Triode (with diode, heptode or hexode) ·Diode-Diode-Triode
L21DD
Battery double-diode triode for receiver detection and audio-frequency amplification. The paired diodes provide signal and control-voltage rectification while the triode supplies useful gain and current drive from a low-voltage filament supply.
- Sections
- 3
- Base
- -
- Socket code
- -
- Base pins
- -
- Nominal heater
- 2 V / 100 mA
Description
Battery double-diode triode companion type printed with HL21DD.
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- -
- Socket code
- -
- Base pins
- -
- Nominal heater voltage
- 2 V
- Nominal heater current
- 100 mA
- Parallel heater voltage
- -
- Parallel heater current
- -
- Series capable
- No
Terminal pinout
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
Section ratings
3 physical sections, each with unique specifications.
Section 1
Diode
No fixed ratings are recorded for this section.
Section 2
Diode
No fixed ratings are recorded for this section.
Section 3
Triode
- Plate resistance
- 10000 Ω
- Transconductance
- 0.00185 S
- Amplification factor
- 18.5
- Max plate voltage
- 150 V
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.