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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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  • 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 Ihmhi ( 1206036 ) <> on Wednesday May 23, 2012 @05:33PM (#40093759)

    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 John3 ( 85454 ) <> 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. :)

  • by Anonymous Coward on Wednesday May 23, 2012 @05:47PM (#40093927)

    Uh... Microwave ovens use a magnetron [] I've repaired many a Microwave ovens and I have never seen any vacuum tubes.

    Too smart for your own good. A magnetron [] is a vacuum tube []. Not all vacuum tubes are transparent. Hell, the "vacuum tube" in the article has neither a tube or a vacuum!

  • by Anonymous Coward on Wednesday May 23, 2012 @05:47PM (#40093935)

    As long as we're quoting Wikipedia:
    The cavity magnetron is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field.

  • by digitig ( 1056110 ) on Wednesday May 23, 2012 @05:53PM (#40093989)

    Uh... Microwave ovens use a magnetron []

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


    Indeed they do use magnetrons. And to quote from the first line of the Wikipedia article on magnetrons" [] "The cavity magnetron is a high-powered vacuum tube..." (my emphasis). Do you repair the microwaves with your eyes closed?

  • 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 scharkalvin ( 72228 ) on Wednesday May 23, 2012 @05:56PM (#40094029) Homepage

    Actually an open heater was NOT the way most tubes died. The coating on the cathode that emits electrons when heated gradually decays and emission drops off to the point that the tubes transconductance is too low for it to operate. But the heater rarely burns out, at least not in indirectly heated tubes. Another way they die is that air gradually leaks in and the vacuum becomes too poor. The silver flashing on the side of the tube will then turn a milky white as the chemical "getter" that absorbs air has absorbed all that it can. Once the getter coating is depleted the tube will become gassy. A tube can also die from shorts when closely spaced elements break loose from vibration and touch. Over heating will soften the elements and cause the same effect. Tubes can handle a much higher percent of overload than solid state devices however. Tubes computers were never faster than solid state ones even if the tubes themselves were faster. Because of their size the total wiring in a tube computer is much longer than in a solid state system. In transistors it is the "holes" in the crystal structure that "move" and the speed of light in silicon is lower than in a vacuum for electromagnetic waves. Still these waves have less distance to propergate in an IC than a bunch of interconnnected tubes. Finally note the description of this new tube technology, it is really a "vacuum state" IC. I always wondered when nanotechnology would be applied to thermionic "valves" (as they say across the "pond").

  • by compro01 ( 777531 ) on Wednesday May 23, 2012 @06:00PM (#40094063)

    No, space is a far far harder vacuum than anything we can currently manage on-planet.

    A vacuum tube still has between 1 million to 1 billion molecules per cubic centimetre, depending on tolerances. The best vacuum we can currently make has about 100k molecules per cubic centimetre.

    Interplanetary space has about 10. Interstellar space has about 1. Intergalactic space has about 1 per cubic metre (10,000 cubic centimetres).

  • Re:Amps (Score:3, Informative)

    by Alien Being ( 18488 ) on Wednesday May 23, 2012 @06:46PM (#40094599)

    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. []

  • by Pentium100 ( 1240090 ) on Wednesday May 23, 2012 @06:49PM (#40094627)

    So, why not combine dozens (or hundreds) of transistor output stages to get the equivalent of a single valve-based amplifier? That way, you get the same output power, but you never need to replace any burned-out tubes.

    Because then the circuit would be much more complex (the need for matching all the small transmitters so they all work well in parallel) and a failed transistor could result in a lot of failed transistors. Tube circuits are simpler and tubes can tolerate overloads better.

    Oh, and another thing. HVDC substations replaced their mercury valve rectifiers many years ago because new silicon-based technology could do the same job, at the same power level, with much less hassle. That's a higher level of power than broadcasting.

    As the result of a rectifier is DC, it is simpler to combine a lot of smaller components in parallel and they dissipate less power than a transmitter would (since the output devices have to operate in linear mode in a transmitter, while they are on or off in a rectifier)

  • Re:Amps (Score:2, Informative)

    by Anonymous Coward on Wednesday May 23, 2012 @07:08PM (#40094809)

    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 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 []

  • Re:Amps (Score:2, Informative)

    by camperdave ( 969942 ) on Wednesday May 23, 2012 @07:59PM (#40095185) Journal

    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.

  • 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.

  • OFFTOPIC: Moderation (Score:4, Informative)

    by rjames13 ( 1178191 ) on Wednesday May 23, 2012 @08:19PM (#40095319)

    Thanks for modding me down jackass. You could have INFORMED me of that fact without punishing me with a -1 whip. (And if it wasn't you, then I direct my comment to the other fucker that did it.)

    You can't post and moderate in the same article. Posting removes all your moderations in that article.

  • 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.
  • by smpoole7 ( 1467717 ) on Wednesday May 23, 2012 @09:09PM (#40095707) Homepage

    > At low power levels (e.g. 10kw) transistorised VHF/UHF output amplifiers are fine. Additionally, you can get a higher power output by operating multiple VHF/UHF output amplifiers in parallel - which also gives some redundancy for transmitter maintenance.

    See Pentium 100's reply; he hit the high points. But it's essentially a matter of cost-effectiveness. If you tell me, "I need 30,000 watts at 100 MHz (a typical FM arrangement), I'm going to use a tube. Even after paying $5,000 for the tube and building a 10,000 volt, 5A power supply, I'd still come out ahead. Combining enough 100-200W solid-state modules to get that kind of power level would be far more expensive.

    There's a practical matter, too -- for example, or 50 KW AM stations *do* use solid-state, and they're done as Pentium100 describes: you combine bunches and bunches of modules to get that power level. That's at a much lower frequency, and they can be made very efficient .. . .. but with full modulation, our Nautel transmitter runs a 300V primary supply and draws in excess of 300 amperes(!). There are giant 3/0 cables (they look like booster cables!) running all over the inside of that thing just to handle the current.

    Can't cheat physics: power = voltage times current.

    But I'll add this: Some competitively-priced solid state high power transmitters have begun appearing, so I have hope for the future. (We're looking at some of the new Nautel FM units ourselves; if you're curious.) But seriously, even as recently as 2 years ago, there was no question that a 4CX20000 tube in a tuned cavity was far more cost-effective than trying to do it with solid-state.

  • 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.

  • by theshowmecanuck ( 703852 ) on Wednesday May 23, 2012 @10:25PM (#40096137) Journal
    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 (now that Putin has installed himself as supreme soviet, is Russia still non-communist?). For example two major tube makers, Sovtech and SED Tubes are both based in Russia. Most of the North American tube makers sold their equipment to folks in these countries. The tube makers who didn't just scrapped everything. I am pretty sure even GrooveTube are made off shore in one of these countries now.
  • by shutdown -p now ( 807394 ) on Wednesday May 23, 2012 @10:52PM (#40096337) Journal

    former communist states (now that Putin has installed himself as supreme soviet, is Russia still non-communist?).

    I dunno how a person can be a "supreme soviet" (soviet = council; "supreme soviet" was the name for the parliament of most communist countries). Anyway, Russia is still decidedly non-communist, since it has full-fledged private property on everything including means of production. It's an authoritarian capitalist country, much like Spain and Chile were back in the day.

  • Re:Pure marketing (Score:5, Informative)

    by Ellis D. Tripp ( 755736 ) on Thursday May 24, 2012 @10:52AM (#40099743) Homepage

    The tube on the AOpen mobo was a 6DJ8/6922, not a 12AX7.

    The 6DJ8 is also a dual triode, but it has much higher transconductance because it is a frame grid design. Those tubes were widely used as input amplifiers in vintage Tektronix scopes because of their low noise and high linearity.

Logic is the chastity belt of the mind!