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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 Toe, The ( 545098 ) on Wednesday May 23, 2012 @05:18PM (#40093591) the phrase "a series of tubes."

    • To quote the now very happy Space Pirates:


    • by mcgrew ( 92797 ) *

      To "incorrect". I'm referring to the summary, not your post. First, vaccuum tubes never went away. Look inside a Marshall guitar amp and you'll see tubes. Grandma's old CRT TV has a tube; the CRT is a tube. Second, "the predecessors of the silicon transistor" isn't inaccurate but may be misleading, as the two operate in completely different ways and have completely different strengths and weaknesses. Heat and overvotage will kill a transistor, but won't bother a tube at all. OTOH, tubes are physically fragi

  • Sweet (Score:5, Funny)

    by Hatta ( 162192 ) on Wednesday May 23, 2012 @05:19PM (#40093605) Journal

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

    • by aix tom ( 902140 )

      Dang. Have to undo botched moderation so I have to come up with a moderately witty reply. ;-)
      So, how about:

      Yeah, you can. But the backpack with the cooling system might get heavy.

    • But can you have one in your transistor radio?
    • You laugh, but I would *love* to have an AM radio in my MP3 player. So far I have not found any..... now maybe with microtubes, it will be possible.

      • My cell phone has an AM/FM radio in it, it also plays hours and hours of mp3s. So I'd say it's already possible and in a lot of places. If you want something specific, the Motorola Photon here in the U.S. but it is far more common on European model phones.
      • You laugh, but I would *love* to have an AM radio in my MP3 player. So far I have not found any..... now maybe with microtubes, it will be possible.

        That's what the fillings in your teeth are for, dude...listening to AM radio and the voices of the aliens telling you what to do.

    • 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. :-)

      • I remember that, they put it onboard and reduced the PCI slots because they assumed you wouldn't buy a soundcard.

    • I bet Jobs could have sold iTube powered iPods and could have made people believe they sound better.
    • by jiriw ( 444695 )

      MP3 player? I want a Pip-boy with 'em tiny tubes!

      And a reservation for a room in Vault 101 to go with it.

    • Re:Sweet (Score:5, Informative)

      by hairyfeet ( 841228 ) <> on Wednesday May 23, 2012 @08:03PM (#40095223) Journal

      They modded you funny but any musician will tell you for guitar amps you can't beat tubes. as a bassist I prefer my Trace solid state (one of the last Brit made before they got bought by Peavey) because its hard to get a truly clean tone out of a tube but frankly that is what makes them great for guitar as even a "clean" tube tone has a warm slightly compressed midrange that is just better than solid state.

      Let us just all hope that Russian Sovtek factory never goes out of business or rock would be screwed. I have heard just about every kind of modeling amp out there but none of them compare to the tone of a Marshall Plexi or a Fender Bassman or Concert, hell even a mid 70s Peavey Mace tube head sounds better than the modeling amps. Sometimes the older tech is just better, that's all.

      as for TFA I'd love to see something like that filter its way down to musical applications. Can you imagine a tube amp you could just throw in a rack and that would take as much abuse as a solid state? man that would be like heaven.

      • 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.

        • Sorry if i got your panties in a wad but I wasn't going with groupthink, i was simply describing what it sounds like to me as a musician that has been playing for 30+ years now. To me tubes DO have a 'warm" sound whereas the solid state amps have a "harsh" tone. Sorry if my not getting all technobabble pissed you off friend, but that is how it sounds to me. if you don't believe me you are welcome to fire up any decent Fender tuber, say a Bassman or Concert or Champ and see for yourself, the midrange has a n

    • With 460GHz capability, the treble should be truly excellent.
  • Amps (Score:5, Informative)

    by Aeros ( 668253 ) on Wednesday May 23, 2012 @05:21PM (#40093633)
    These are still widely used in some of the best amps out there.
    • by John3 ( 85454 ) <john3@cornells . c om> on Wednesday May 23, 2012 @05:35PM (#40093781) Homepage Journal

      And they are used in some of the best old-school reel-to-reel recorders. I don't know if they are making new components with tubes, but older tube pre-amps for Ampex and Scully tape recorders are prized by some audiophiles for their "warm" sound. They are also great for creating distortion...over-driving tube pre-amps creates some nice distortion effects which digital components would just clip.

      But (and I'm speaking as someone who has been out of radio and audio for many years...I own a hardware store), from what I've seen and heard there are some pretty awesome digital programs that can duplicate nearly any pre-amp ever made. Based on what my daughter can do with her Mac (Protools, FInale, etc) I am pretty impressed at the sounds that can be processed even in a home environment with no need for tubes.

      On the other hand, my tube pre-amps do keep the basement warm. :)

    • Re:Amps (Score:5, Insightful)

      by EdZ ( 755139 ) on Wednesday May 23, 2012 @05:45PM (#40093905)
      Most expensive, maybe, but best? Not if your goal is a transparent amplifier: one that takes an input, and reproduces that output as accurately as possible with a higher amplitude. Valves suck at this. An entire branch of mathematics (control theory) was developed to compensate for the horrendous non-linearities of vacuum tubes.

      You may like the distortions produced by tube amps (or transistor amps outputting those same distortions via DSP), but don't pretend they're better at reproducing sound. They are demonstrably not.
      • Re: (Score:2, Insightful)

        by Panoptes ( 1041206 )
        Tubes (or valves, as they were known in the UK) had one big quality advantaqe - noise level. A valve amplifer could produce dead silence: tranny amplifiers, even the best, had a faint but audible slushy hiss.
        • 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: (Score:3, Informative)

        by Alien Being ( 18488 )

        You have that backwards. Tubes are inherently more linear than transistors. Transistors have small ranges of linear operation and require complex bias control and feedback for audio use. In addition, the harmonic distortion of tubes is primarily even-order which sounds smoother than the odd-order harmonic distortion of transistors. []

        • Re: (Score:2, Insightful)

          by Anonymous Coward

          I find it interesting that the wikipedia page cites some marketing material by a tube amp vendor as the source for that info. I guarantee if you speak with someone who has designed high-power amplifiers with both tubes and transistors they will consistently tell you the transistors are the only way to go for accurate reproduction.

          One of the biggest problems with vacuum tube designs is that it is very hard to keep impedance linearity across the 20-20khz spectrum. When you are trying to drive a speaker whic

        • Yep, that detail may be right. But transistors achieve a much higher gain (even more when you couple several of them), what lets you put them in bias control and feedback circuits. Inside those circuits they are way more linear.

          The final result is that transistor based amplifiers are (nearly without exception) more linear than the tube based ones.

          • Re:Amps (Score:5, Informative)

            by jenningsthecat ( 1525947 ) on Wednesday May 23, 2012 @09:30PM (#40095809)

            Yes, transistor audio amplifiers are "way more linear" with gobs of negative feedback applied, if THD, (Total Harmonic Distortion), is your measurement criterion. ANY amplifier is more 'linear' with correctly applied negative feedback. The basic premise is that added harmonics are bad - if you feed a pure sine wave into an amplifier, you want a pure sine wave at the output. The problem is that in audio, THD is a fundamentally flawed measurement with very poor correlation between lab measurements and listening tests.

            THD measurements are taken as the ratio of the total power of all harmonics to the power of the fundamental, with no weighting of any kind applied. The trouble is, human hearing doesn't respond to harmonic distortions in this linear fashion - our ears find higher order harmonic distortions much more apparent and objectionable. []. This deficiency was noted by prominent BBC engineers D.E.L. Shorter and Norman Crowhurst in the 40's and 50's, when they proposed weighting harmonics by the square or the cube of the order; but their voices were drowned out by market forces that wanted a simple, flattering figure of merit that made the newer, more powerful pentode-based amps, (with lots of negative feedback), look better on paper than their lower-powered triode predecessors. The market won out over scientific and technical accuracy, (it usually does), and today engineers the world over, ignorant of this history, mistakenly believe that low THD is the gold standard for measuring and defining audio amplifier quality. (For a good technical analysis of distortion and the sound of an amplifier, see Lynn Olson's excellent investigation. []

            By the way, in the 'tubes vs transistors' debate, good triodes have the advantage of being more intrinsically linear than transistors. This means that they require less negative feedback to tame their distortion, and often sound wonderful with NO negative feedback. The THD figures of amps built this way are often quite poor, but look at their spectra and you'll see predominantly second- and third-order, with a smooth and rapid falloff of higher order harmonics. Occasionally solid-state amps can give this kind of performance, but tubes have an easier time of it. Designing a good-sounding, (as opposed to good-measuring), audio amp, requires a lot of skill, and a lot of knowledge about distortion mechanisms and how to counter them. Unfortunately the prevailing practice in HiFi is to add more gain, throw most of it away with additional NFB, get a nice low THD figure, and call the job done. Amps designed this way generally sound like shit, if not initially, then after 20 minutes or so of listening, at which time listening fatigue sets in.

      • The same control theory that was developed in the tube era is applied to an even greater degree in transistor based amplifiers.

      • Rarely, if ever, is anyones goal a transparent amplifier. Especially when it comes to actual instrument amplification. Tube amps produce superior sound in almost all situations. A transistor, when clipping, literally squares off the top of the wave. A Tube will still clip but does so gradually, producing a more rounded wave form. Basically when clipping a transistor sounds horrendous... you must always operate a transistor well bellow its clipping threshold (hard to do with analog instruments) where as the
        • Re: (Score:2, Informative)

          by camperdave ( 969942 )

          Basically when clipping a transistor sounds horrendous... you must always operate a transistor well bellow its clipping threshold (hard to do with analog instruments)

          Sounds to me like they are using the wrong sized transistor.

      • They're a simple solution for guitar amps where the distortion is intentional..players can fiddle with the bias to get the distortion they want.

        Also there's an inherent capacity to deal with large overloads and high powers as compared to transistors.

      • A good modern transistor amp can do precisely what a good amp should: Disappear. They can have distortion low enough, noise low enough, be linear enough, and so on that they don't introduce any audible artifacts of their own. You can swap well built ones around and hear no difference.

        That's what you want out of a good reproduction amp, just a wire with gain effectively. It should introduce no changes of its own. Of course you can't have one that is flawless and does NO changes but you can have one that the

      • Fidelity and appealing sound are different issues. Most old school recording engineers hated digital recording at first because it didn't sound as good as analog tape. They deemed that digital was inaccurate and blamed it on flawed methodology, "rounding errors" etc. But the fact is that the tape, like tubes, were coloring the sound artificially in a pleasant way while digital was only trying to be neutral.

        Nowadays, tape is pretty much dead, tube-based recording consoles are pretty much non-existent, as

    • 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.

      • Re: (Score:2, Informative)

        by Anonymous Coward

        The hum was actually caused by the caps being too large. Try an additional 50 or 100 uF caps and you'll see what I'm talking about.
        Power supply caps are generally sized by the rail current they're strapped to, stating in simple terms. Their should also be some very
        small ceramic caps (.01 or .1 maybe) to clean up/filter the high freq noise. Remember, it's really an AC circuit you're working with; I
        think the idea of big caps came from enhanced after-market car stereos - which are a true DC circuit.

  • 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.
    • Re: (Score:2, Informative)

      by Ihmhi ( 1206036 )

      Don't forget guitar amps. You're not gonna get the same aesthetics out of silicon. The best amps all pretty much use vacuum tubes.

    • by Bill, Shooter of Bul ( 629286 ) on Wednesday May 23, 2012 @05:53PM (#40093991) Journal


      The amplifying triode vacuum tube was invented near 1907.
      The transistor itself in 1947.

    • by n6kuy ( 172098 )

      ...and linear proton accelerators. Vacuum tubes are still used [] for particle accelerators.

    • by mirix ( 1649853 ) on Wednesday May 23, 2012 @07:21PM (#40094897)

      A lot of microwaves have a vacuum tube for the display too.

      (The erie blue-green ones) VFD []

  • by Anonymous Coward on Wednesday May 23, 2012 @05:25PM (#40093673)

    aren't they just called "tubes"?

  • by Dr. Tom ( 23206 ) <> on Wednesday May 23, 2012 @05:32PM (#40093729) Homepage

    low power, high frequency, rugged, ... I say, these things might be useful

  • It mentions that the scale of these things is 150nm, which sounds pretty large compared to modern cpu features. Still, it's a very interesting development.

  • by eclectro ( 227083 ) on Wednesday May 23, 2012 @05:50PM (#40093965)

    There is 1) no vacuum and 2) there is no "tube." While there is an electron emitter, this device should be called a MOSFET.

  • 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

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

      Well, maybe not so much a classic vacuum tube, since electrons are generated through field electron emission, not thermionic effect. It does look similar to some cold cathode devices though, like neon lamps or maybe plasma display cells. The interesting parts are the very small size and the addition of the gate which allows modulation of the electron flow.

      Makes me wonder if tunneling plays a part here

      Maybe a bit, but AFAIR electron tunnelling happens at really small scales, in the sub-nanometer range, maybe up to a few nanometers. The gap mentioned in

  • Really? This is pitiful.
  • Vacuum tubes went the way of the dinosaurs in the 1960s

    Cutting the summary writer some slack, ignoring audiophile amps, ignoring guitar amps, ignoring microwave ovens, ignoring broadcast equipment, and even ignoring cathode ray tubes (which still outnumbered flat panel sales through 2004), consumer television sets didn't go "solid state" until 1975 (I remember it being a big deal to have the "solid state" badge on the front of a new-fangled TV because it meant you didn't have to wait (as long) for it to war

    • by mirix ( 1649853 )

      Many sets were already hybrid or entirely solid state by '75.

      GE kept making the portacolor [] until 1980 or so, but it was the last of the tubed sets (In North America anyway - I imagine Soviet sets were still tube for a while yet, but maybe not). I presume GE just rode out the existing tooling, and when the portacolors finally quit turning a profit/selling they tooled up for more SS sets (or got undercut by Japanese SS sets, either way)...

      Though as I've mentioned earlier in this thread, any TV with a CRT isn'

  • 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:The Tube Dance (Score:4, Informative)

      by rubycodez ( 864176 ) on Wednesday May 23, 2012 @08:40PM (#40095485)
      easy to do for anyone who could follow the instructions that were on the machine and quite clear. sad she had to pay money, the Radio Shack ones were free. I used to collect TV and radios that were stood by the garbage cans the night before collection day for my electronics hobby, did the "tube dance" as a kid. Yes, I did solid state (discrete and integrated) based experiments and creations too.
  • I love the way the big snag is barely mentioned near the end of the article. They need about 10V to power up. That makes them rather unsuitable for Terahertz computing.
  • Vacuum tubes aren't that unusual. The US Military has been using them for decades for Night Vision equipment and the best NV equipment is still based on vacuum tube technology. This is what Image Intensifiers are, which comprise more than 90% of new NV equipment.

    Less commonly ( and more historically ) the Image Intensifier is a particular type of tube known as a photodiode, but more modern tubes incorporate a lot more technology including electron multipliers ( microchannel plates ) within the tube itself.


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