Faking A Hollow State Device

There’s been a resurgence of interest in vacuum tubes. Even if you do think audio sounds better through a tube, you have to admit the care and feeding of filaments and plate voltages isn’t trivial. [Ed Nisley] decided to sidestep all that and just build an objet d’art that looks like a tube.

A burned out halogen bulb stands in for the tube, and a ceramic base holds the bulb. It also conceals–what else–an Arduino. The Arduino drives a knock-off Neopixel LED hidden in a faux plate cap. The result is a glass envelope bathed in a cold blue and purple glow that changes under software control.

We’d really like to see this kind of tube inside some rebuilt piece of tube gear. Or maybe Korg should offer LED lighting options for their recent tube in a chip form factor. If you really want to be a top-tier tube hacker, you can always try your hand at repair.

30 thoughts on “Faking A Hollow State Device

    1. I prefer tube amps mostly because their design is trivial and amenable to tinkering (by adding or altering caps say at the anode resistor o bypass it). Added to this is the general low part count and lack of small parts.

      Doing so safely is another matter I suppose.

  1. Not sure what the point of this is, it certainly looks nothing like a tube.
    But please, can you stop calling everything WS8211/WS8212-based a “neopixel?” I know you’re best friends with adafruit, and that’s okay and totally fine, but the constant refering to their products gets annoying quickly. Also, and this is even more relevant, it makes searchiing impossible. If I get a strip of WS8212 LEDs and I want to be inspired about what I could do with them, I might search for WS8212 on hackaday. This doesn’t return anything “neopixel” though. So please, if you are referring to a product that’s basically just a glorified breakout board for a chip in an article, could you please also put the actual name of the chip in the article?

    1. If you read the article you’ll see they refer to them as neopixels everywhere including the arduino library. The name was used and kinda stuck. You’ll just have to accept it. In fact, based on the article, I don’t see which part it really is.

      1. Still it’s not like anyone here doesn’t know that it just means “WS2812”, just because you see a “Neopixel” in a project doesn’t mean you’re gonna get one from Adafruit.

        It’s kind of a stupid cutesy name but it’s more memorable in a world where everything has 2 letters and a number.

  2. This is nothing like a real tube. Oh, I s’pose it is made of glass and has something in it, and a glow…
    The color of the LED is wrong, unless it is a mercury vapor rectifier, or you have a crook tuber, and then the glow is in the wrong place.
    Why not get a real tube and stick an orange LED in the base? That would look better.
    My first amp was a tube type, many years ago. They are fun to build. In a weak moment I gave it away. It is a pity as I would like to be able to show it to my grand kids.
    Just if you are going to build a tube amp, just remember, they can bite!

    “Good Things Come In Glass, Not Epoxy Resin” :)

    1. ^This.

      This is an interesting 10 minute art project, but that won’t fool anyone who has ever seen a real vacuum tube in operation.
      Besides, why fake it? It’s not like real vacuum tubes are hard to source these days. A few minutes searching Ebay and you’ll have a lifetime’s worth of old audio amps to repair and polish. Then you can sit back and pretend that they sound better than modern amplifiers.

      1. Heh!

        I dunno why you need an LED at all. If you just want something nice to look at, get yourself a tube, any old tube, and put 6V on the heater. Lovely orange analogue glow.

  3. That defunct halogen bulb happened because I had it lying around; they picked the worst picture and cropped it far beyond what the resolution would support.

    I’m also working through my box of vacuum tubes by setting them in 3D printed sockets:

    They look surprisingly good with bottom & top illumination:

    And, yeah, when the red light comes on in the base, they look just right…

  4. Blasphemy !!! Poser !!!

    What next ? “restoring” a vintage 57 Chevy by installing a touch-screen NAV radio ?

    Tar and feather him, and run him out of town on the rails !!!

  5. I have about 30 tube amps in this room and more in the basement. They’re (fairly) easy, and fun to work on because the circuits are ridiculously simple. Real tube amps turn out to be much less complex than fake tube amps made with solid state devices. Though if you know how to bias a FET down into the nonlinear region you can get harmonics similar to a single ended tube amp stage.
    Eventually I’ll publish a headphone amp with a tube for gain, tone control and a solid state power amp section, all powered off of 5V USB. Switching boost power supplies are great.

    1. Please do. Making them is a hoody of mine for those exact reasons.

      Often you have more parts in a FET follower than the rest of the valve amp (power supply included)

    2. Aussie Dave does a nice tear down of a “valve” headphone amp. He was half-expecting the valve not to be in circuit at all. In the end, it turned out it was, as a simple voltage follower, feeding into a couple of op-amps that did the actual driving.

      The valve was run at 12V plate voltage, and basically wasn’t really amplifying in any useful way. Purely there to claim the sound went through a valve. The way it’s wired up, I’m pretty sure it won’t have the valve “sound”.

  6. Best ‘fake’ tube: 0A3 regulator. It’s a neon gas filled regulator tube which you can run off 120v AC, along with a diode and a 2W 5K resistor in series. It looks like a real tube (because is it) and it has a really good orange glow in the center.

  7. Best fake tube: 0A3 regulator. Use off 120V AC with a diode and 5K 5W resistor in series. Looks like a real tube (because it is) and has an awesome orange glow in the center. They’re under $10 each and the socket is cheap too.

    1. I have a number of the different voltages of these. It would be easy to make them blink with a cap and resistor just like little neon bulbs. Not that tubes do, but it’s the art. In old Conn amps the reg tube does dim and sorta blink when you hit the bass.

    1. A really interesting idea, that book series. It goes into how do you preserve as much of your tech as possible within your limited knowledge base and resources. Also how to adjust to never being able to go back to your own time and place, while fitting in to a completely different social environment. I recommend these books. Quite a good yarn!

  8. Blue isn’t just the wrong color for a vacuum tube; as everybody who’s worked on tube gear knows, a blue glow means that the tube is gassy, and therefore BAD.

    1. Also it’s truly horrible to the eyes, especially at night. Blue leds should never ever be used for anything that is being turned on in the dark.

      There are really cheap and beautiful amber leds available online; they give the exact luminescence one would expect from a tube or an analog panel meter.

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