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Science Hardware

Return of the Vacuum Tube 313

sciencehabit writes "Peer inside an antique radio and you'll find what look like small light bulbs. They're actually vacuum tubes — the predecessors of the silicon transistor. Vacuum tubes went the way of the dinosaurs in the 1960s, but researchers have now brought them back to life, creating a nano-sized version that's faster and hardier than the transistor (abstract). It's even able to survive the harsh radiation of outer space."
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Return of the Vacuum Tube

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  • by mpoulton ( 689851 ) on Wednesday May 23, 2012 @05:22PM (#40093643)
    Almost every TV broadcast transmitter and most FM radio broadcast transmitters still use vacuum tubes for the high power output stages. Every microwave oven uses a vacuum tube to produce the microwaves. Most radar transmitters use vacuum tubes for the output stages, and often for signal generation too. The fact is that semiconductors have simply not been able to catch up to vacuum tubes for high power applications at UHF frequencies and above. 1960's technology still reigns supreme.
  • by Anonymous Coward on Wednesday May 23, 2012 @05:38PM (#40093811)

    Uh... Microwave ovens use a magnetron

    I've repaired many a Microwave ovens and I have never seen any vacuum tubes.


  • Re:Sweet (Score:4, Interesting)

    by Dogtanian ( 588974 ) on Wednesday May 23, 2012 @05:52PM (#40093983) Homepage

    Now I can have a tube amp in my mp3 player.

    Well, they released a motherboard around a decade back with integrated vacuum tube based audio. []

    I remembered this as being a separate soundcard, but I couldn't find reference to anything like that online, so I might have been wrong. Still, given that onboard audio isn't- or at least wasn't back then- generally considered to be the best (i.e. not what the audiophiles would have gone for), this seems like a strange mix. As if the valve/tube-based PCI card wouldn't have been weird enough, mind you. :-)

  • by Cochonou ( 576531 ) on Wednesday May 23, 2012 @05:54PM (#40094009) Homepage
    From a radiation engineering point of view, outer space is not the most stringent environment. It is actually significantly more forgiving than a lot of useful earth orbits or the radiation belts of the gas giants (but of course, you can hardly replace a failed transistor in space...).
    These "vacum tube like" diamond field emission devices have shown radiation tolerance from 10 to 100 Mrad (1 MGy in SI units), so we are more talking about the levels required for operation in nuclear reactors or close to the beam of particle accelerators.
  • by dpilot ( 134227 ) on Wednesday May 23, 2012 @06:14PM (#40094227) Homepage Journal

    "Tales of the Flying Mountains" by Poul Anderson

    It's a collection of short stories about the "Asteriod Republic" wrapped in a frame of the first interstellar flight. One of the stories features a military vessel whose electronics were built with "TEMMs" - Thermionic Emission Micro-Miniaturized - featured for its radiation hardness.

  • O... M... G... (Score:4, Interesting)

    by JamesP ( 688957 ) on Wednesday May 23, 2012 @06:22PM (#40094331)

    The article is painful in some aspects

    Electrons move more slowly in a solid than in a vacuum, which means transistors are generally slower than vacuum tubes; as a result, computing isn't as quick as it could be.

    I'm flabbergasted.

    Meyyappan, who co-developed the "nano vacuum tube," says it is created by etching a tiny cavity in phosphorous-doped silicon. The cavity is bordered by three electrodes: a source, a gate, and a drain. The source and drain are separated by just 150 nanometers, while the gate sits on top. Electrons are emitted from the source thanks to a voltage applied across it and the drain, while the gate controls the electron flow across the cavity

    This is really a vacuum tube if you add a high dose of immagination. Really

    The separation of the source and drain is so small that the electrons stand very little chance of colliding with atoms in the air

    Makes me wonder if tunneling plays a part here

  • Soviet Russia (Score:5, Interesting)

    by Anonymous Coward on Wednesday May 23, 2012 @06:33PM (#40094453)

    When Viktor Belenko defected to Japan with a MiG-25 fighter jet in 1976 (state of the art Russian aircraft back then, meant to counter our F-15) it was discovered that most of the electronics onboard the aircraft were built with micro-miniature vacuum tubes! The reason being that the fighter jet was designed for presumably nuclear war situations, and the Russians wanted to ensure that EMPs from nuclear explosions would not permanently damage the electronics, so the aircraft could still fly and fight even after exposure to any nearby nuclear explosions that were still distant enough to not physically destroy the aircraft.

  • Re:Amps (Score:5, Interesting)

    by Zordak ( 123132 ) on Wednesday May 23, 2012 @06:44PM (#40094569) Homepage Journal

    <memorylane> One of my lab partners in my EE Lab class played bass guitar. He wanted a tube pre-amp, but didn't want to spend $1,000 for it. So we built one as our lab project. We pulled a transformer out of an old Hammond organ, pulled tubes out of some old random stuff in a cabinet in the lab, threw in a pair of 12,000 uF caps, and four ceramic diodes for the rectifier. Then we had to code our own SPICE model for the tube so we could simulate it. That was one stout amp. Except the transformer put out a really unstable power waveformm, so one of our ceramic diodes exploded (tripping a breaker and taking out power in that wing), which was actually kind of cool. But we had to find a different transformer. Another time I accidentally grounded the 600-V node, which blew a big hole in our trace line and evaporated the solder off of one of our caps. The edges of the trace line survived, so we soldered the cap back in, powered it up, and it worked great. It was perfect except we were never able to get rid of the 60 Hz hum when it was plugged in. If you unplugged it, you could play for about a minute before the caps drained, and it sounded spectacular.</memorylane>

    I miss those days. Now I just sit around writing patents and pleadings all day.

  • The Tube Dance (Score:4, Interesting)

    by Tablizer ( 95088 ) on Wednesday May 23, 2012 @06:46PM (#40094593) Journal

    When I was a young kid, my mother would fix the TV by pulling out all of the TV tubes, wrapping them in news pages, and then carrying them all down-town to a big drug store which had a coin-operated tube-tester machine. She'd plug them into the matching slots one by one and see which ones were good and which were sour. I couldn't help her because I was too short.

    Then she'd go to the back of the store to find matches for the sour tubes based on the codes printed on the tube slots. (Often the label was worn/cooked off the tube itself such that the slot labels on the tester were the only way to tell.)

    I'd generally consider her a "technophobe", but she did it in a very routine fashion as if she'd done it dozens of times before. People just got used to tubes back then.

    At least TV's were partly repairable. Now the repair costs are often more than a new TV. Oh, and Get off my lawn!

  • Re:News for who? (Score:5, Interesting)

    by BlueStrat ( 756137 ) on Wednesday May 23, 2012 @07:54PM (#40095157)

    I believe that anyone younger than 30 now stands a damn good chance of never seeing a vacuum tube or even know of their existance.


    If they ever attend a rock concert or watch a video of one (or if they ever take up electric guitar or bass) they'd see walls of them. Usually with big script logos that say "Marshall" or sometimes logos that say "Fender", "Soldano", or "Mesa-Boogie", with a few other brands that are less well-known and typically considered more "exclusive" like Matchless, Framus, Dr. Z, Top Hat, Divided by 13, Bad Cat, Victoria, etc etc.

    All the top guitar-amplifier makers' top-of-the-line pro-level models brag of being "all tube". DSP has not yet been able to equal the tone, "feel", and response to the player's nuances that vacuum tubes exhibit. It's really, REALLY hard to model all the variables that affect the sound of an electromechanical device like a vacuum tube with digital signal processing.

    I build and sell custom vacuum-tube guitar amps myself, as well as provide service and repair for vintage & modern tube guitar and bass amps. I can also occasionally be found on a stage in a club, or on a festival stage somewhere, playing guitar. I've been doing both for about 4 decades now.


  • Re:Soviet Russia (Score:4, Interesting)

    by _merlin ( 160982 ) on Wednesday May 23, 2012 @08:12PM (#40095265) Homepage Journal

    Sorry to be a whiny bitch, but the MiG-25 was actually designed to shoot down the XB-70 Valkyrie []. The XB-70 project may appear to be a failure in that it only produced two prototypes at enormous cost, but it achieved what it was supposed to in that the USSR spent a fortune building a fleet of interceptors to shoot it down.

  • by PaulBu ( 473180 ) on Wednesday May 23, 2012 @08:18PM (#40095317) Homepage

    And the funny thing that it was even not that "secret" of a technology (application was, of course!), I remember reading about "new life of a vacuum tube" in Soviet magazine for technically-inclined kids ("Yunyi Technic" []) sometime in my early teens, late 70s - early 80s -- I definitely remember reading about thin-film integrated vacuum tubes technology, and, I think, about it's rad-hardness (not using that word, of course, or better half of the reason why it is important ;-) ).

    Paul B.

  • Re:Soviet Russia (Score:5, Interesting)

    by careysub ( 976506 ) on Thursday May 24, 2012 @01:40AM (#40097077)

    Your post and the GP's post are in agreement, I think. The XB-70 Valkyrie was designed to drop nuclear bombs on Soviet cities. The MiG-25 was designed to shoot it down. If one XB-70 dropped a nuclear bomb, and the EMP disabled the transistor-based radars of all nearby MiG-25s, then the other XB-70s would be able to reach their targets unmolested. So the MiG-25 radar was built with vacuum tubes instead.

    And in addition, it was a tremendously powerful radar - 600 kilowatt continuous beam - well beyond the capability of solid state electronics of the day.

    It was an extremely well designed radar system - it is hard to see how any possible design of the period could have improved upon its many advantages.

  • Re:Amps (Score:5, Interesting)

    by Anne Thwacks ( 531696 ) on Thursday May 24, 2012 @02:00AM (#40097145)
    As the former road manager of several well-known bands (in the 1960's) I can state with absolute confidence that the reason we bought valve amps (or copied the well known Vox design ourselves) was that they did not blow up if overloaded. Early transistor amps were not very robust, and typically burned out during gigs.

    *AFAICR Vox, Fender, Orange, etc all uses the exact same circuit - the valves and transformers came from different suppliers, and some of the metal work was a different shape.

  • Re:Sweet (Score:5, Interesting)

    by thegarbz ( 1787294 ) on Thursday May 24, 2012 @03:25AM (#40097499)

    Actually it's far more technical than some fuzzy "it sounds warm" bullshit you hear from audiophiles. When you overdrive a tube they have a natural tendency to round over slightly rather than hit a hard limit and flatline. This is similar to tapes which could be recorded above their maximum 0dB point. This creates an interesting form of compression and combined with distortion / overdriving creates a sound that is very difficult to replicate with solid state stuff.

  • by K. S. Kyosuke ( 729550 ) on Thursday May 24, 2012 @03:57AM (#40097621)

    Since there aren't any vacuum tubes (valves for our European brethren) being made in North America anymore, guitar amp parts suppliers source new tubes from Russia and other communist (i.e. China) or former communist states

    Hah, they probably would have done in anyway. These amps often leave the tubes visible from the outside to increase the coolness factor of the device and I can't think of many more effective ways of making it even cooler than having the tubes have strange, exotic shapes and threatening-looking Cyrillic writings on them.

  • Re:News for who? (Score:5, Interesting)

    by BlueStrat ( 756137 ) on Thursday May 24, 2012 @04:02AM (#40097629)

    It has more to do with reputation than with "can't be done otherwise". A 50 cent-a-pop DSP probably has enough power to simulate the good ol' vacuum tube sound.

    Well, I guess we'll have to agree to disagree here. For 40 years I've worked at music stores and been in bands, never mind being an amp tech/designer/builder, even worked in avionics and military-related high-end electronics systems, heard many of the very best DSP studio rack processors made costing many thousands of dollars, and my ears and everything else I know and have learned so far during all this time convinces me that, although DSP has gotten much, much better compared to even 5 years ago, it hasn't arrived yet at the point where the human ear can't tell the difference.

    DSP guitar tone, clean or overdrive/distortion/effects, does not sound like real tubes *yet*. They will probably get there, I'm not saying it won't happen, maybe quite soon. It's just not there yet.

    There's one solid-state amplifier made starting in 1975 that sounds great for jazz guitar. The Roland JC-120 Jazz Chorus 120 amplifier. Beautiful clean sounds. It does have a distortion function, but *nobody* used it once they heard it! :)

    Don't get me wrong. If you're in a local small-town working bar/dive band that is mostly there for the $40 to $80 a man per night, and not trying to impress anyone with your tone except the bar owner...just enough, that is, to pay you and keep you on the booking rotation, and you don't want to carry any more than absolutely necessary nor tie up more money than you absolutely have to in an amp, something like one of the "Line 6 Spider" combo amps will "get it done". Sorta like when old people...well, never mind. :-/

    Those type of DSP solid state amps are also great for those just starting out, as it has a bunch of effects in software already, no effects pedals or rack effects, cords, etc to bother with, and they're dirt-cheap as amps go. If it breaks, throw it away and buy another just like a disposable lighter.

    And yes, I do prefer the vacuum-tube amps, not only because of the sound, but also the warm feeling of old electronics :)

    Here's my personal amp that I built recently. []

    4 tubes total. two 12AX7 dual-triode preamp tubes (one a parallel-triode preamp gain stage, the other is the "long-tailed pair" style dual triode inverter/driver tube) and two KT66 beam tetrode power tubes in cathode-biased push-pull Class AB, producing around 30 watts. Volume and Tone controls, Standby/On and Power On/Off toggles. That's it. It sounds fantastic. You can't find a Volume/Tone control setting combination that sounds bad. I keep finding wonderful new tones and sounds almost every time I play it.

    The sealed-back dovetail pine cab finished with Tru-Oil gunstock finishing oil with a Baltic birch plywood baffle has a pair of Celestion G12T-75 12-inch 8 Ohm guitar speakers wired in parallel for a 4 Ohm total impedance. It sounds absolutely gorgeous. Combined with that amp, some serious guitar tone-heaven.

    I took the amp head into the local Guitar Center store shortly after I'd finished it. They had *nothing* that sounded anywhere near that good. The manager finally noticed the small crowd gathering, and (gently) asked me to cease after he started hearing a couple people asking if I sold amps like that one. :D

    Oh, and since you mentioned a "warm feeling from old electronics", here's a little something that's sure to make wherever it is at just a little warmer. And louder. A *LOT* louder. [] [] [] []

    And, in case you couldn't read that huge brass meter at the top. []

    Yes, that's 5 kilovolts (5,000 Volts) on the tube plates. Watch the fingers near the pretty tubes now, kiddies! :P


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