Old TVs, early supercomputers, and modern fancy sound equipment all use vacuum tubes. But why? What does a vacuum tube do?
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A vacuum tube can do similar things as what semiconductors do today.
The simple function is a diode, it only allows current trough it in one direction. A more complex but also more useful function is as an amplifier. A small input current can control a large output current. This is what transistors do and what is used in amplifiers and computer applications.
The first vacuum tube was made in 1904 and it was a good. The first semiconductor are made in 1940 but it is not until 1960 that transistors start to replace vacuum tubes for applications like television and radio receivers. It was at that point that got cheaper.
Vacuum tubes have been and are to some degree still used in some applications where semiconductors have problems iwh the power levels. The high-power amplifier in TV or radio broadcasts, radar systems etc.
But for many other applications like computers semiconductors are superior. The last vacuum tube computer was made in early 1960.
Audio is another usage. The harmonic they create especially if you overdrive an amplifier. You get even-order harmonics with tubes but even-order harmonics with transistors. You can listen to the difference in https://www.youtube.com/watch?v=RUpvAdF3M2M
This is for simple amplifiers. You can build a digital system that creates distortion like tubes do if you just do not over the amplifier. There is a lot of stuff audiophiles do and purchase that makes no difference if you do a blind test, very expensive cables that claim to have special properties are an example. They even have claims for digital cables which it can have no effect at all, they are just a scam.
Tube amplifiers are in large part because most of them will not be driven so you get distortion, so a way companies try to make more money. It is not a total scam because there is a difference but in practice, it do not have a noticeable effect for most. The main advantage is you can boast about your amplifier to your friends.
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