The Plasma Speaker




About: ––––––––––––––––––––––– "Energy cannot be created nor destroy...

Are you tired of those old black speakers that only just make sounds? Maybe sound reactive lights are just not enough to impress you? How about a Plasma Speaker?

A plasma speaker is a device that generates an high voltage electrical arc that makes purple light and music! Without any speakers or any moving parts! Sounds too good to be true? Well, you're wrong, the high voltage arc really does 'sing' by vibrating in the air. (Of course, you will need to give the device musical audio for it to work.) And just leave this instructable if you still don't believe me...

And this is something I always wanted to build - I have been dreaming to build one for about 6 months, until Kiteman has greatly boosted my encouragement to build one. (Thanks Kiteman!)

The video of my plasma speaker - early prototype.

Step 1: The Dangers You Must Know...

A plasma speaker is no toy...

Health Hazard
Unlike the ordinary speakers, the plasma speaker are dangerous high voltage device, do NOT attempt to build this device unless you know what you are doing... And do NOT even attempt to build one if you have heart problems or weak heart or wearing a pacemaker, because one little shock from this thing can put you out...
I am not responsible for any injuries or deaths caused by this device.

Why should you know all of this? it is because you can ONLY live once, and no more...
If you don't think that you shouldn't build one, just watch movies of it working instead, much better than risking your life to build and operate one.
If you think you are okay to build one without killing your self, then move on to the next step.

Hazard to Electronics
Since the plasma speaker generates high voltages, there is a chance there will be high voltage spikes on the low voltage side of the device, which can get onto the audio line and damage (or destroy) the player. They are some safety features to prevent the spikes damaging the player, but they can fail... So I am not responsible if your player gets damaged, and use cheap players like CD players, if you're rich, you can use expensive players if you want. :-)

Step 2: Schematics

I got the idea from scopeboy's website on his flyback driver section, but the schematic was quite complex and buying four MOSFET's is a little too expensive for me...

So I simplified the design to using one MOSFET.

I get a lot of complainants of this project is not working very well or at all. This new design WORKs, however, for most people it may not work. This is due to the MOSFET (and some other components) is poor quality.

I just recently found out that manufacture who makes the components sell the best quality ones to other manufactures and sell the poorer quality ones to the whole sellers and retailers. For this project, the best grade MOSFET's is critical, and it can only be gotten by salvaging old electronic devices, unless you are willing to pay for thousands of components for the manufacture... :-)

Step 3: So, How Does It Actually Work!?!?!?

Okay, you must be very curious how the plasma speaker works...

Note: This information is technical, skip this step if you don't understand...

The TL494 acts like an oscillator and a modulator, it generates a high frequency (5KHz to 45KHz) to drive the flyback transformer to make high voltage arcs. Then when you give it audio, the TL494 modulates the audio frequency into the main high frequency. Now the flyback transformer is being driven by the high frequency and the audio frequency, and when the arc is produced, the arc vibrates the air with both the audio and high frequency creating sounds.
If you tune up the 22K potentiometer, the high frequency increases, when it goes higher than 20KHz, we cannot hear it, but only the audio frequency...

I hope you can kinda understand this..

Step 4: What You Will Need...

You will need quite a lot of stuff to make the plasma speaker...

  • TL494 chip (Datasheet for TL494)
  • 200uF (or 220uF) - 50v electrolytic capacitor
  • 47nF - 250v (or similar voltage ratings) capacitor
  • 100nF - 50v capacitor
  • 10nF - 50v capacitor
  • 2.2K - 1/4W resistor
  • 10 ohm - 1/4W resistor
  • UF4007 diode (or other fast diode that is rated 1A (or more) and 500v (or more)
  • 10K - 1/4W potentiometer (same thing as a variable resistor)
  • 22K - 1/4W potentiometer (same thing as a variable resistor)
  • Audio jack
  • Wires
  • IRF540 MOSFET (other MOSFET's with similar ratings should work)
  • Large heatsink
  • Flyback transformer (can be found from old CRT.)
  • 12v power source (for TL494 oscillator / I used a 9v battery)
  • 12v to 40v power source (for the flyback transformer)
  • Breadboard (for testing)
  • Veroboard

I bought most of my electronic parts from Farnell.

  • Soldering iron
  • Wire strippers
  • Wire cutters
  • Pliers
  • Helping hands
  • Hot glue gun

  • Good with a soldering iron.
  • Can read schematics.
  • Know what you are doing when you are dealing with high voltage.

Step 5: Build the Prototype on the Bread Board

Do what the title says... Build the circuit on the bread board!

Why on a bread board and not build it directly onto the veroboard?

Well, it is a very good idea to build the prototype on the bread board before you solder the components onto the veroboard because...
  • You will get a better idea on how to build a 'real' one on the veroboard.
  • You can make sure all the components are working fine, if not, you can replace it easily.
  • You can modify or tweet the circuit a bit to give the plasma speaker a better performance.

I built my circuit using my simplified schematic on the bread board that is connected to the "Electronic Lab" kit that I got a long time ago.

To connect the flyback transformer to the circuit, wind 5 or more turns of thick solid-core wire on the ferrite core. That will be your primary coil.

Step 6: Test the Prototype

After you had built it, go ahead and test it!
If it does not work, don't get all frustrated or anything like that, go back and check your circuit closely, make sure there are no missing connections, and check the components are properly connected to the circuit...

Mine works quite well, unfortunately, the MOSFET is wasting large amounts of energy into heat, so it is blazing hot... I have to make the heat sink bigger to try keep it cool longer. But it still goes blazing hot after three minutes of continuous operation.
Oh well, that is my efficient design so far...

If yours working well with out very much problem, thats great!

Step 7: Build the Circuit

After you have tested to make sure everything is working, start building the prototype onto the veroboard.

If you notice in the pictures, I use an 16 pin socket for the TL494, it is really good idea to use sockets for the IC' s because you won't risk heat damage from soldering, and if the IC fails, you can easily replace it instead of desoldering it and solder another one in..
I also added an LED indicator, that is a good idea to add that on too, so you know whether the circuit is on or off. The LED indicator is connected to the TL494's power supply line.

After you had done soldering, make sure you made nice shiny solder joints and they are no solder bridges. If you think it is all good enough, add some dab of hot glue onto the loose components and wires for strain relief.

Step 8: Final Test

Okay, you are very close...
Test your plasma speaker to make sure if it is working or not.

If its working, let out a sigh of relive that you did it!

If its not working, don't overreact of frustrated, (I know it is very frustrating when something does not work).
A few things can go wrong with this circuit, here is a list of some problems...
  • Solder bridge - That is the most common problem in soldering.
  • Some connections missed out - Also another common problem...
  • Damaged components
Try find and fix the problem, there is no point giving up - unless you are really lazy to do so...

After you got your plasma speaker working, it is a good idea to the circuit into a project box. I will protect the electronics from being damaged from foreign objects and protects people from an electrical shock.

Step 9: Enjoy and Impress Your Friends!

Well, there is the instructions to make your own Plasma Speaker! Go ahead and pump in your favorite music then listen and watch the arc dance with the music and admire what you had built...

Then show it to your friends and family, I can guarantee you they will be greatly impressed.

When my Dad first saw my plasma speaker in operation, his first words about it are: "What the f... Tha... Thats impossible." He is wrong, nothing is impossible... Nothing.

Step 10: How to Use the Plasma Speaker

Here is how you can control the plasma speaker with the two potentiometers.

The 10K potentiometer is used to change the TL494's internal oscillator frequency - from 5KHz to 50KHz. If you want to play music on the arc, tune the frequency up until you don't hear it and play the music. Note: The 10K potentiometer does NOT affect the input audio (music).

I am not too sure what the 22K potentiometer's job is, but it seems to change the volume of the audio, fiddle with the 22K potentiometer until you can hear the music loudly. Note: Making the music louder will shorten the length of the arc.

Step 11: Interesting Discharges...

Just a little story I like to tell you about...

While I was testing (well, playing) my plasma speaker, the 12v battery is going flat and the arcs are becoming unimpressively short. So I replaced the battery with my lab PSU I modified from an ATX PSU and put an 22,000uF capacitor in parallel with its 12v output and ground.
The 22,000uF capacitor is used to adsorb any high voltage spikes that may appear on the line.

When I connect the PSU's power to the plasma speaker and turned it on...

The arc are very different, instead of a sting of purple light, the arc flaps furiously and it makes very interesting light display. But this is not suitable for a plasma speaker, because the arcs flaps so much it just simply drowned out the music...

Here is a video of the arcs.

Well, I hoped you enjoyed this instructable!
If you have any questions, or need help, or found an error, or anything, make a comment! I like comments! :-)

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1,510 Discussions


3 years ago

Nice project! I think one reason your MOSFET is running hot, and that some people might not be able to make this work is that there is nothing to actively drive the gate low during the off phase of the PWM so it takes a while to switch off, which makes it dissipate a bunch of power as the MOSFET (source to drain) resistance is between on and off.

You should be able fix this by using the second transistor (Q2) of the TL494 to pull the MOSFET gate low during the off part of the PWM. To do that, you'll need to connect C2 (pin 11) to the resistor that drives the MOSFET gate, and E2 (pin 10) to ground.

Also, be sure to wire OUTPUT CTL (Vi, pin 13) to Vref (+12v) so that you enable push-pull operation of the TL494's two transistors, Q1 and Q2. Otherwise they'll be exactly in sync (on at the same time) instead of exactly out of phase (one on when the other is off), and the circuit mods I suggest above would burn out your TL494!

To be sure, I'd like to put an oscilloscope on the gate of the MOSFET to see how quickly it turns off, but it sure looks like it would turn off slowly and run hot as-is.

1 reply

Reply 2 years ago

Agree. the mosfet's gate should be discharged in the off state. I'm quite surprised this could actually work even without the normal tl494 driver transistors for discharging the gate.


2 years ago

Sweet speaker! Just read another Ible where the builder used 2 MOSFETs wired parallel to keep the temp down- his was operating at 70c, with heat sink and a pc fan- thought that might be helpful for your heat issue.

Marco MicrOchipA

3 years ago

Hi, great Project. can you tell me the name of that kind of electronics experiments box ?

1 reply
SirCooksalotMarco MicrOchipA

Reply 2 years ago

That's a Radio Shack Electronics Learning Lab. But there's all sorts of free plans out there for simpler homemade versions- google 'breadboard tester' or 'DIY breadboard station',maybe just 'DIY breadboard'


3 years ago

Can I use a 33nF 400v capacitor instead of the 47nF capacitor? If not, i) is there any way I can find this component in broken electronics, and ii) is there any substitute capacitor with a different capacitance for the 47nF capacitor?
I might daisy-chain 2 or 3 capacitors to get the desired capacitance with the specific voltage. I know this question sounds silly.


3 years ago

The last video doessays: "this video is private"

1 reply

Reply 3 years ago

Same here. :(


3 years ago

Decades ago I seen something like this.

An arc moving to music. At the time it was high science and cutting edge stuff. I am glad it is within reach of the average person now as it would make a great experiment for the cautious and intelligent :)

Keep up the good work :)


3 years ago

I just love this and Tesla would be soooooo pleased.

Others may have mentioned this (the comments are many <sigh>), but this is also known as a 'singing arc'--how cool is that?

William Du Bois Duddell was the Electrical Engineer that first conceived the idea in the early 1900's. He was quite ingenious and would have loved Instructables.


3 years ago

Just a little side note: the Smiths were a great music to test it out with!

1 reply

Reply 3 years ago

I gotta disagree...Morrisey's got a four, maybe five major-scale note-fixation, which I find grating at best, so probably not the best choice for a demo track.


3 years ago

That is quite possibly one of the coolest things I've ever seen.


3 years ago

This is so cool!! How loud does it get? And what is the sound quality and frequency response like?


3 years ago

Pretty lights, but don't look at them - plasma generates enough ultraviolet light to burn your retinas out...

3 replies

Reply 3 years ago

Good point but what if the arc is enclosed in a traditional speaker box after removing the speakers themselves. Yes the fabric speaker grills will need to be retained. Perhaps doubled up too to prevent leakage of UV.


Reply 3 years ago

My little knowledge of plasma speakers is they are higher frequency and might disappear in a box - think of them as tweeters (?)

Given that, maybe UV blocking glass? Flat black V with a plate in front, like

\ /
\ X /
\ /

X is the plasma, the rest a sort of open, vertical horn.....

You've got a beautiful display potential, maybe make the front panel out of the UV glass? That'd probably be a lot cheaper and easier to find, too.

You'd want a fairly full spectrum blocker - I expect these things spray a LOT of RF, but don't know that for sure. Any AM radio will help you find that out.

I'll bet that plasma is hot enough to ignite most flammable material, so unless you can experiment, I'd avoid cloth!

Best of luck with this - I hope it works out for you!


Reply 3 years ago

Agree with all that Kev13. Like the idea of the UV glass for the visual effects too. The RF spectrum could be contained in a Faraday Cage? Close woven 'chicken netting' stuff? lined on the inside like the acoustic wadding. Or metallised paint. Thanks for the vertical horn Idea Kev13.


3 years ago

why do you use 5 turns of wire instead of the primary pins on the transformer base ?


3 years ago

Excellent stuff. Exactly the sort of project I follow Instructables for. Different, very interesting and do-able.