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  • Need amp builder help

    Before getting lost in the quagmire of web searches, I thought I would start with the experts here.

    I am making plans for a sculpture using tubes. I would like to use a variety of 10 tubes. I would prefer them to light up. Without making an amp, how can I get 10 random tubes to illuminate? I'm not looking to make a reading lamp, this is just an art piece. I would like to give it a subtle glow.

  • #2
    Place small orange LED's behind them. That way you aren't dealing with high voltages in your sculpture.
    GTWGITS! - RacerX

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    • #3
      It only takes 6 volts to light up most tubes (6V6, 6L6, 5881, EL34, KT 66, 77, 88 or 90)...etc.
      12 in series for 12XX tubes.
      Very old tubes with 50, 35, etc numbers in the prefix require those voltages to light up.

      I may have some very cool old tubes you might be interested in.
      Bulb styles, etc.

      Radio shack would have a 6.3 volt transformer that would work, or you
      could use one of those 6V lantern batteries.

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      • #4
        Another possibility is to take the voltages of all the tube, and add enough to equal 120 volts. This way you can have them all light up without buying a heavy transformer. If you go over 120, it will be less bright. Under 120, and it will be brighter and may have a shorter lifespan.

        For example, you can connect 10 12AX7's in series to come up with a perfect 120 volts.

        I have built an amp using 2 12AX7's, a 50C5 output tube and a 35W4 rectifier. I had to also use a power resistor to drop the additional voltage.
        Last edited by DonP; 03-29-2013, 02:10 PM.

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        • #5
          Doing the math, if I used 20 tubes, then approx it would be 120 v. With all those pins, how do you properly connect 20 tube sockets together? Maybe I should watch "City on the Edge of Forever" and see how Spock did it? If I can get these tubes connected correctly, is the rest of the wiring as easy as a desk lamp?

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          • #6
            You'd still want some kind of isolation transformer.
            That's a classic "Widowmaker" circuit.
            Extreme shock hazard, and problematic if a tube filament burns out.

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            • #7
              Try to find an OA3 regulator tube if you want some real lighting.
              They really do give off this much glow, not sure about current draw.
              And the current is one thing you are going to have to consider in this project.

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              • #8
                Originally posted by Cygnus X1 View Post
                You'd still want some kind of isolation transformer.
                That's a classic "Widowmaker" circuit.
                Extreme shock hazard, and problematic if a tube filament burns out.
                You know, I thought so as well. But my isolation tranny wasn't up to snuff and ran hot so I removed it. No loss and it's been running fine for 20 years.

                Many cheap tube amps were made like this (Harmony and I forget the othe brand)

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                • #9
                  The issue here isn't going to be high voltage, but high current.
                  a 5U4 can pull 3 amp, plenty enough to kill.
                  IDK if that's just to run the filament at idle or under load though.

                  I'll take that question to some amp builder's forums for you, and get back.

                  Other consideration is how are you going to wire it?
                  Sockets or hard wired?
                  What is the general structure of the sculpture?

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                  • #10
                    I do not want it to be a hazard to myself or others. If a tube fails, I do not want it to burn up the whole thing.
                    I was thinking about sockets so that tubes could be replaced. The base of the sculpture can function as a housing for the transformer, etc. The emphasis will be the subject matter, use of tubes, the lighting effect. Basically it is an "art from found materials" project.
                    BTW - I found an artist who does this art too. He reveals no construction secrets.

                    Designing original art is like trying to write an original song. Just when you think you have discovered something unique, you can find someone else on the internet who has already done it.

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