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Really Really Small Vacuum Tubes
  [vote for,

I'll start by pointing out that valve is a British term for vacuum tube, and that that we couldn't call small tubes nanotubes because that term is already in use. (I think nanotubes are very long threads of fullerene or something.)

Actually, this isn't so much a proposal as wondering if it would work and if it would offer any advantages.

I know that people go to extra trouble and pay extra money for audio devices with vacuum tubes, particularly home audio amplifiers and guitar amplifiers.

It also seems to me that the technology for making really small things has improved since the point in time when conventional wisdom decided that vacuum tubes were passe and transistors, later integrated circuits, later chips, were the way.

So, could our current technology produce, say, a vacuum-tube iPod? And would we want to? Are there audio purists who don't like "the transistor sound" who'd like a personal audio player with tubes?

I'm just guessing, but I'd think a small enough tube (1) wouldn't require too much power to make this feasible, (2) wouldn't get too hot to be used, and (3) wouldn't take the 20-30 seconds to warm up that my old table-top radio with inch-and- a- half long tubes used to take. Or am I wrong? Would a tube iPod necessarily drain four AA's in a half-hour and get hot enough to burn its way out of a shirt pocket? And am I wrong about the possibility of manufacturing vacuum tubes the size of a Tic-Tac (or smaller)?

What does anyone think?

cranford, Jan 05 2006

PDF FILE: A Micromachined Vacuum Triode Using a Carbon Nanotube Cold Cathode http://repositories...&context=postprints
"fully integrated on-chip vacuum microtriode using carbon nanotubes as field emitters" [half, Jan 05 2006]

Nanotube radio http://www.physics....anoradio/radio.html
[jutta, Jul 14 2008]

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       Great idea, I'm afraid I don't know the answer - [angel] will probably know as he's quite valvey. My only concern is that during the period they were making valves they also made flashlight bulbs which were around 10% of the size of the valves. If they could make filaments and glassware that size, wouldn't they have shrunk the valves if they could? Just a thought.
wagster, Jan 05 2006

       Thanks for finding the "Micromachined Vacuum Triode" document. The other part of my question is would anyone buy a "tube iPod?"
cranford, Jan 05 2006

       'Are there audio purists who don't like "the transistor sound" who'd like a personal audio player with tubes?'   

       The answer to the first part of that question is yes, so the answer to the second part is probably the same. (If the NanoValves produced the same purist pleasing harmonics/distortion/warmth as produced by an ordinary vacuum tube)
half, Jan 05 2006

       //would anyone buy a "tube iPod?"// Yes. Definitely. Even if it sounded exactly the same as a transistor iPod.
wagster, Jan 05 2006

       The even harmonics produced by a traditional glass-envelope vacuum tube, such as the American 12AX7 dual triode, don't seem to be quite as present in ceramic-envelope tubes. I haven't heard a good explanation for this, and I'm not sure you'd get the same effects with what amounts to a carbon envelope.   

       Also, there's the concern of miniaturizing tubes down to the scale of modern transistors or smaller - at that scale, I'd think a thermionic device would behave so much like its semiconductor counterparts as to sound like the same thing.   

       The equipment wouldn't necessarily have to be hot or power-draining, as you can easily make a cathode with a coating of thorium and eliminate the need for filaments altogether.   

       They've made some pretty small tubes in the past. I have a Victoreen radiological survey meter, Cold-war vintage, with a very small electrometer tube inside, good for 100+ hours of operation on a single D cell battery.   

       + for the idea of a tube iPod. I'd buy one, assuming I could even afford the plain vanilla semiconductor version.
Headcleaner, Jan 05 2006

       In my teenage garage-band days, I got to play with some nice tube amplifiers. Sweet noise.
normzone, Jan 05 2006

       A tube ipod would double as a pocket handwarmer. Might need BIG batteries as tubes take a LOT of current!!!
Minimal, Jan 06 2006

       They make your hi-fi glow in the dark
hippo, Jan 06 2006

       //Remind me, what are the real and desirable advantages of using valves in audio?//
Crank a Les Paul up with a Marshall valve amp and check out the broken distortion!. Much nicer!
gnomethang, Jan 06 2006

       //what are the real and desirable advantages of using valves in audio?// It's to do with the electric, it needs more room to move about in the wires, and valves probably provide both that, and a warming heat source by which a sepia tinted 1940's family can cower around while they listen to the soothing, sonorous voice of the Home Service telling them that everything is all right.   

       In addition, valves are more likely to remain viable after the emp blast of a nuclear weapon, so if you want to listen to the radio or your iTunes after the apocalypse, valve technology really is for you.
zen_tom, Jul 14 2008

       {looks at iPod}   

       Hmmm. Suddenly you don't seem so new and hip anymore.
MikeD, Jul 14 2008

       "Remind me, what are the real and desirable advantages of using valves in audio?"
Purists perfer the sound - however I think that's when you're dealing with an analog source (record/tape). I don't think there'd be any improvement using MP3s. And the whole kit would get very warm.
phoenix, Jul 14 2008


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