Singing: With Plasma!

While there are many ways to produce audible sound, Plasma Speakers have to be one of the coolest. Usually very complex and expensive, we received a tip for a beginners guide to making one of these impressive novelties. Handily included are a set of schematics (one very simple schematic, the other with a few artistic illustrations). There are also a set of warnings, which include sound advice to mind the heat generated by the MOSFETs, as well as making sure that your input signal isn’t too strong. The finished product is fun to listen to, so be sure to check out the example video after the break.


44 thoughts on “Singing: With Plasma!

  1. :D I have the parts to make this. Well I was planning to make some plasma tweeters for a while now. I picked up 2 of the 15kW inverter board from a X-Ray machine a while back, they have 16 800V mosfets on them each. Actually it’s pretty well everything in that circuit except for the driver chip.

    Anyways one quick question/thought. Did you remove the HV diode on the secondary of the flyback transformer? I would imagine if you didn’t it would add quite a bit of distortion to the audio being reproduced. I was planning to go the tesla coil route, but figured it would end up ‘ringing’ which would also ruin the sound quality. I need to find one of the old flybacks without the diode potted inside.

  2. @Fallen
    The drone you hear on Tesla coil audio is caused by the spark gap in the primary circuit which causes a relatively low square wave modulation of the high frequency secondary oscillation.

    To hide the drone, keep the frequency of the ringing up above human hearing and more than 2x the max frequency of the sound you want to reproduce. 48KHz would work well.

  3. @Grenadier,
    I still have them, I ‘obtained’ (my manager told me I could keep them) them from one of my employers a few years back. I was working for an OEM in the RMA department, and these came back with some blistering between the fiberglass weave on the PCB. We decided scrapping them was cheaper than reworking(especially since IIRC the multiplier boards they drove got up to 100kV, so it was important that the insulating ability of the PCB wasn’t hindered.).
    Unfortunately I don’t have the multiplier boards. I sure did repair a lot of them though :).
    It was a fairly standard circuit they used, just a cockroft walton(sp?) multiplier, in parallel with a 1W 10MR resistor. There was also a second multiplier on some boards for filiments or something, I can’t remember. Oh and a couple resistors in a voltage divider to monitor the voltage out.
    The boards had slots routed in them between HV parts, and everything was immersed in oil.
    The company they were made for was CPI, but I don’t know the exact product/products it was used in.

    I’m going to hang onto them as I’m a class D nut.

    Honestly the real reason I haven’t went forward with it is ozone production. It’s nasty stuff, and I haven’t figured out a cost effective way of building the tweeters and doing away with ozone production. :) using argon or helium would be way too expensive.

  4. László Monda not to mention that the sound quality is terrible.

    daman this is just a high voltage power supply

    when it is connected to a vacuum tube of sort whether it is a crt or a laser tube or a light bulb or vacuum tube based rectifier diode it will produce xrays.

    grenadier i think ozone is produced from anything that ionizes the air.

    i guess if ozone can damage your work you could try using some cfcs to destroy the ozone like collect the freon from old air conditioners.

    the problem is you have a spark that may turn the cfcs into phosgene witch is deadly

  5. @Grenadier: Congrats on being featured twice on HAD in a single day, and still having a functioning server!

    In case it’s useful, some options for AC output from a flyback:

    1) Some people have successfully drilled/dremelled into their transformer just before the diode to tap into the unrectified output; but success rate seems substantially less than 100% (I tried once and failed).

    2) Old TVs that use separate voltage triplers have no rectifier in their flyback. Exactly how old (and large) a TV you’d need, I’ve never found out.

    3) Or just buy a new flyback without a rectifier. Check out “FLYEXP” at “” for a nice assortment which includes some non-rectified ones. There may be other sources, it’s been more than a decade since I’ve looked.

  6. Yeah I’ve got a great server. I think engadget might kill it though…


    I know that, In fact I’m using an AC FBT in my next project…

    After 30 minutes there is still not a hint of O3 in the air.

  7. About the circuit, is this a good way of driving mosfets? Also there is an absence of a snubber to damp the reverse kick. The protection diodes in the Mosfet look to be working over time.

    Isn’t the IRFZ44N a better option? do we really need a 200V Mosfet here?

  8. Very nice project! I actually heard one of the “original” plasma tweeters – the Ionovac – many years ago and this was great to see. Those DuKane or ElectroVoice Ionovacs sell for big $$$ these days, perhaps you could make a marketable modern version?

  9. This thing has to produce a lot of ozone. I did a great deal of research on this exact subject, and after less than a minute you could clear smell the ozone the arc is producing. And really who wants a fire hazard stereo combo? Sure the blue light is mesmerizing for the first few minutes, but after that all you will be left with is a space full of stanky ozone.

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