The last several decades of technological progress have, in large part, been about finding more and more things we can do with semiconductors and the technology for producing them.
Vacuum tubes have another specific modern use: in amplifiers, where their non-linear behavior at higher temperatures can create everything from a "warm" sound (with added harmonics) to the "distorted" sound associated with electric guitars. Musicians pay extra for vacuum-tube amplifiers. Even technologies that fall out of widespread use can still have artistic uses or even become luxury products.
It's like the way incandescent bulbs are still used for warmth and atmosphere. (There was an IEEE review of a vacuum tube iPod amplifier that pointed out that vacuum tubes, unlike other electronics, when overloaded still produce warm and wonderful sound.)
Photomultiplier tubes (mostly produced by Hamamatsu Photonics) can detect individual photons and have some crazy applications, like the Super-Kamiokande neutrino detector, as well as more pedestrian but super useful ones like blood analysis.
Relatedly, vacuum florescent displays were in production for automotive use as late as 2008. They were bright enough for sun adapted eyes to see.
As a clutzy hobbyist formerly working on power audio and RF HF power it's fair to note that vacuum tubes are rugged. They tolerate/d overload on a human time line, unlike most semiconductors which fail before they glow red.
Vacuum tubes are surprisingly tough. They were used in ordinance as proximity fuses back in World War II. Having broken a few in my day, I'm amazed they can be shot out of a cannon.
I still have a couple of nuvistors lying around, good at UHF and used in the space program, early on. Not quite cannon fodder, but would possibly survive a big rifle or Howitzer shot.
One of the older techs at a company I worked for had been involved with the TIROS satellites, the first weather satellites. They had iconoscope tubes in them. He said those tubes had to be rotated regularly, kind of like riddling champagne, lest their delicate structures become deformed by gravity. I was surprised. After all, the whole point was to blast them into outer space on a rocket. I guess there are different kinds of toughness.
My "year" through tertiary education in the early 1970's was the last to be taught primarily in valve theory. Due to hysteresis in the wider aviation industry and "gummint" budgeting I managed my 30 year career with limited exposure to semiconductors by transitioning from valves (and relays, lots of relays) to integrated circuits and then to signal processing using computers.
Ukrainians recently displayed fragments of the Russian "Oreshnik" MRBM, and mocked the use of "ancient technology" in the form of vacuum tubes.
The laughted died down when the explanation that vacuum tubes are used for their resistance to the EMP effects expected of nuclear-tipped interceptor missiles was revealed.
“Cambrian explosion”. I like that phrase. It perfectly characterizes so many (all?) important lines and branches of discovery while acknowledging the similarity to natural selection.
There has been work on and off in the past 15 years on sub-micron sized triodes for THz and radiation resistant electronics. Oddly, they can be so small that they do not require vacuum, with the distance between the cathode and anode being less than the 70 nm mean free path in air. See https://www.mdpi.com/2072-666X/10/12/858, for example. Also the work of Srisonphan and Meyyappan beginning at UPenn in 2009.
Commercial uptake seems absent, it has mostly been research.
Another "use" of vacuum tubes, if you want to call it that, is to prepare a very fertile ground for subsequent semiconductor technology.
Diodes and triodes (the latter eventually called "transistors" in the semiconductor domain) were the key technology for much of the electronic devices in the late 19th and early 20th centuries. Not only did they lay the theoretical and practical groundwork for a wide range of devices, and motivate the development of the relevant mathematics, but the shortcomings of vacuum tubes (mostly size, heat, power consumption, and short lifetimes) created an immense technological hunger which would be rapidly satisfied by solid state devices. Indeed, it's not obvious that the latter would have been interesting at all if vacuum tubes were not discovered first.
ENIAC, one of the early modern digital computers fabricated from thousands of vacuum tubes, made plain the immense potential of electronic switching technology, but also made plain the impracticality of vacuum tubes beyond a certain size and complexity. Would digital computers now exist if vacuum tubes hadn't laid the groundwork? Perhaps not.
Photomultiplier tubes are still in common use for physics experiments; they have a number of characteristics that make them better than their semiconductor counterparts for very low-noise, high-sensitivity requirements.
This is a classic example of what David Edgerton calls 'the shock of the old.' It’s a great reminder that technological success is measured by decades of use-cases, not just the date of invention. Highly recommend his book by the same name if you're looking to dive deeper into why certain technologies refuse to be 'disrupted.'
I am highly interested in the manufacturing of vacuum tubes. I think it is a technological wonder not to break the fragile glass while creating such large pressure difference. Or is it filled with inert gasses? I don't know...
Some tubes are sealed by heating the top while pulling the tube so as the soft section stretches it also shrinks to make a smaller tube. Then that tube is connected to a vacuum pump. The elements inside the tube may at this point also be baked for a while to drive off surface impurities, then part of the thin tube is heated to collapse under the vacuum and make a closed seal.
Other tubes are round-topped like test tubes, molded, and sealed to a separately prepared base of glass while in a vacuum chamber. The sealing can be heat by heating the rim of the tube before pressing it against the base. Glass-to-glass heat-and-pressure seals work best since they do not outgas and spoil the vacuum. This requires more complex machinery than a glass-stretching approach but could be more effective for mass-produced items.
The mid-19th century is when so many modern inventions got their start. Look at the long life of the internal combustion engine invented by Lenoir in 1858. When I was a kid, I read a biography of Morse and was amazed that he had to wrap insulation around his own wires. By the middle of the century, you could just buy insulated wire. It's like clear glassware in the 17th (?) century. It really helps innovation when you can buy the parts off the shelf. Lately, I've been building amazing toys with pieces from the Adafruit catalog. Who knows what we're inventing now.
Vacuum tubes have another specific modern use: in amplifiers, where their non-linear behavior at higher temperatures can create everything from a "warm" sound (with added harmonics) to the "distorted" sound associated with electric guitars. Musicians pay extra for vacuum-tube amplifiers. Even technologies that fall out of widespread use can still have artistic uses or even become luxury products.
It's like the way incandescent bulbs are still used for warmth and atmosphere. (There was an IEEE review of a vacuum tube iPod amplifier that pointed out that vacuum tubes, unlike other electronics, when overloaded still produce warm and wonderful sound.)
One disadvantage of vacuum amps: they are heavy. Lugging them on stage is not anyone's idea of fun.
I never would have known this. That's such a creative use!
Small correction:
> by changing the current in the metallic grid
Umm, no. The voltage of the grid, relative to the cathode, blocks the electrons (or not).
The small(ish) current from the cathode to the grid the does flow when the tube conducts is secondary.
Thanks, fixed.
Photomultiplier tubes (mostly produced by Hamamatsu Photonics) can detect individual photons and have some crazy applications, like the Super-Kamiokande neutrino detector, as well as more pedestrian but super useful ones like blood analysis.
Relatedly, vacuum florescent displays were in production for automotive use as late as 2008. They were bright enough for sun adapted eyes to see.
As a clutzy hobbyist formerly working on power audio and RF HF power it's fair to note that vacuum tubes are rugged. They tolerate/d overload on a human time line, unlike most semiconductors which fail before they glow red.
Vacuum tubes are surprisingly tough. They were used in ordinance as proximity fuses back in World War II. Having broken a few in my day, I'm amazed they can be shot out of a cannon.
I still have a couple of nuvistors lying around, good at UHF and used in the space program, early on. Not quite cannon fodder, but would possibly survive a big rifle or Howitzer shot.
One of the older techs at a company I worked for had been involved with the TIROS satellites, the first weather satellites. They had iconoscope tubes in them. He said those tubes had to be rotated regularly, kind of like riddling champagne, lest their delicate structures become deformed by gravity. I was surprised. After all, the whole point was to blast them into outer space on a rocket. I guess there are different kinds of toughness.
My 2010 Dodge Challenger still uses them for the information displays below the speedometer/tachometer.
My "year" through tertiary education in the early 1970's was the last to be taught primarily in valve theory. Due to hysteresis in the wider aviation industry and "gummint" budgeting I managed my 30 year career with limited exposure to semiconductors by transitioning from valves (and relays, lots of relays) to integrated circuits and then to signal processing using computers.
Thanks for the memories.
I wrote a paper on this in college, perhaps I will find it again one day! Always a fan of the triode, and it's simpler nonlinear behavior.
Ukrainians recently displayed fragments of the Russian "Oreshnik" MRBM, and mocked the use of "ancient technology" in the form of vacuum tubes.
The laughted died down when the explanation that vacuum tubes are used for their resistance to the EMP effects expected of nuclear-tipped interceptor missiles was revealed.
“Cambrian explosion”. I like that phrase. It perfectly characterizes so many (all?) important lines and branches of discovery while acknowledging the similarity to natural selection.
There has been work on and off in the past 15 years on sub-micron sized triodes for THz and radiation resistant electronics. Oddly, they can be so small that they do not require vacuum, with the distance between the cathode and anode being less than the 70 nm mean free path in air. See https://www.mdpi.com/2072-666X/10/12/858, for example. Also the work of Srisonphan and Meyyappan beginning at UPenn in 2009.
Commercial uptake seems absent, it has mostly been research.
Forty years ago in college we used various tubes. Thanks for the memories.
Another "use" of vacuum tubes, if you want to call it that, is to prepare a very fertile ground for subsequent semiconductor technology.
Diodes and triodes (the latter eventually called "transistors" in the semiconductor domain) were the key technology for much of the electronic devices in the late 19th and early 20th centuries. Not only did they lay the theoretical and practical groundwork for a wide range of devices, and motivate the development of the relevant mathematics, but the shortcomings of vacuum tubes (mostly size, heat, power consumption, and short lifetimes) created an immense technological hunger which would be rapidly satisfied by solid state devices. Indeed, it's not obvious that the latter would have been interesting at all if vacuum tubes were not discovered first.
ENIAC, one of the early modern digital computers fabricated from thousands of vacuum tubes, made plain the immense potential of electronic switching technology, but also made plain the impracticality of vacuum tubes beyond a certain size and complexity. Would digital computers now exist if vacuum tubes hadn't laid the groundwork? Perhaps not.
Photomultiplier tubes are still in common use for physics experiments; they have a number of characteristics that make them better than their semiconductor counterparts for very low-noise, high-sensitivity requirements.
This is a classic example of what David Edgerton calls 'the shock of the old.' It’s a great reminder that technological success is measured by decades of use-cases, not just the date of invention. Highly recommend his book by the same name if you're looking to dive deeper into why certain technologies refuse to be 'disrupted.'
Lets not forget about the 'bhangmeter' used for detecting the double-flash of nuclear explosions. It's also named after drugs!
I am highly interested in the manufacturing of vacuum tubes. I think it is a technological wonder not to break the fragile glass while creating such large pressure difference. Or is it filled with inert gasses? I don't know...
Some tubes are sealed by heating the top while pulling the tube so as the soft section stretches it also shrinks to make a smaller tube. Then that tube is connected to a vacuum pump. The elements inside the tube may at this point also be baked for a while to drive off surface impurities, then part of the thin tube is heated to collapse under the vacuum and make a closed seal.
Other tubes are round-topped like test tubes, molded, and sealed to a separately prepared base of glass while in a vacuum chamber. The sealing can be heat by heating the rim of the tube before pressing it against the base. Glass-to-glass heat-and-pressure seals work best since they do not outgas and spoil the vacuum. This requires more complex machinery than a glass-stretching approach but could be more effective for mass-produced items.
Interesting.
The mid-19th century is when so many modern inventions got their start. Look at the long life of the internal combustion engine invented by Lenoir in 1858. When I was a kid, I read a biography of Morse and was amazed that he had to wrap insulation around his own wires. By the middle of the century, you could just buy insulated wire. It's like clear glassware in the 17th (?) century. It really helps innovation when you can buy the parts off the shelf. Lately, I've been building amazing toys with pieces from the Adafruit catalog. Who knows what we're inventing now.