History of the vacuum tubes – Today

history of the vacuum tubes : a 4cx20000

The reign of the thermionic valve did not last forever. Developments in semiconductors resulted in the invention of the transistor in 1948. This meant that smaller, reliable, and less power hungry devices could be made. The success of the transistor was far from instantaneous. It took until the 1960s before domestic radios used them widely. Even then many vacuum tube radios remained (and still remain) in service for many years afterwards. Like any other story, the history of the vacuum tubes will end one day. Today thermionic technology is still used but in limited areas. High power transmitters still use tubes, like the 4CX20000 able to deliver 35 KW in the FM broadcast band. But even in this field power MOS-FET’s are beginning to take market shares.

But to many people, transistors do not offer the same lively feeling as a tube does. They don’t have the warm friendly glow of a valve. To those who worked with tubes, there will never be anything that can equal them.

Production

Since 1964 the famous tube factories like Mullard, Telefunken, RCA, Western Electric or Philips either closed or stopped production of most -if not all- valves. Only high power high frequency tubes were still manufactured. Around 1980 army forces around the world (especially the US Navy, US Army and most of the European armies) started to resell their spare parts of tubes equipments as those were not needed anymore. Hundreds of thousands of tubes, usually manufactured between 1935 and 1965, were made available for the public. Those valves are called New Old Style, NOS in short. New because they were never used, Old Style because those were manufactured long ago. Another steady source of tubes is factories located in the former USSR. Those are producing valves almost (if not totally) identical to those made in western countries between 1945 and 1960. Of course those manufacturers are now using modern technology and materials. Electro-Harmonix, SED and Genalex (Russia), Euro Audio Team (Czech Republic) and JJ Electronic (Slovak Republic) are among the best. The last source for tubes is China. There are dozens of Chineese factories, like Shuguang, manufacturing valves with a quality and reliability ranging from very poor to very good. The SINO brand is a vast improvement over what was available from China just a few years ago.

This ends this small serie of articles about the history of the vacuum tubes. We hope you have enjoyed the reading