Low voltage tube

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A low-voltage tube is an electron tube whose anode voltage is not several hundred volts , as is usual , but which works even at low voltages. It is therefore also suitable for experiments by beginners who do not want to expose themselves to the dangers of electric shock . In contrast to battery tubes, the lowest possible power consumption is not the top priority; low-voltage tubes have heating capacities just like conventional tubes.

Ordinary tubes have a very high impedance , so they only deliver a noticeable current at high operating voltages and thus negligibly little power in the lower voltage range. In addition, their characteristics are very non-linear in the lower voltage range and thus produce strong distortions, if they amplify at all.

Low-voltage tubes were usually designed as ordinary amplifier tubes such as triodes, tetrodes or pentodes , but diodes and mixer tubes were also found.

Development and areas of application

The first transistors had very poor high frequency properties, which continued to require the use of tubes. Since the required anode voltage first had to be generated in a complex manner when used in car radios, for example, tubes such as the ECC86 were developed.

The low-voltage tubes developed for the audio sector also came from the automotive or military sector, where no mains voltage was available.

These tubes were later used in building sets such as the “ Kosmos Radiomann ” due to their simple and safe handling .

Examples of low-voltage special tubes for use in car receivers:

  • EBF83 (IF control pentode with two diode lines for AM demodulation)
  • ECC86 (VHF tension grid double triode)
  • ECH83 ​​(oscillator triode mixed heptode for AM applications)
  • EF97 (ZF control pentode)
  • EF98 (IF and NF pentode)

Examples of low-voltage tubes for power amplifiers:

  • 13P1S (power pentode with 550 mW effective output power (AC voltage) at 26 V operating voltage or 2 W-3 W at 60 V)

technology

The special properties of the low-voltage tubes were primarily achieved through high values ​​for the penetration (or low values ​​for the no-load gain factor). For this purpose, the distances between the electrodes were kept very small, for example through the tensioning grid technology found in the double triode ECC86 .

Web links

Individual evidence

  1. ↑ VALVO Reports Book V 2, pp 35ff., Hamburg 1959