I have long wanted to build a plasma speaker but i haven't been able to find the information about how to do it until now when i stumbled onto this one from Teravolt.org, in the instructions he describes some problems with extreme power loss in the transistor which i have partially solved by using a FET driver to decrease the transition time between on and off states. The transistors will still have to take care of the reverse pulse from the transformer and will therefore still need to dissipate some heat.
I started out by buildning a driver board using the SG3525 voltage to PWM chip and a FET driver, it turned out pretty well, the sound quality was pretty ok, but the volume is low so i decided to build a larger version with 4 arcs and some means of directing the sound, so far i have mounted all the power electronics in a project box and started figuring out how to make the high voltage leads, arc gaps and control electronics.
One thing i knew before hand was that all modern TV flyback transformers have built in rectifiers and therefore only output DC. I wanted to test the difference between DC and AC so i carved into the transformer until i found the end of the flyback coil. After testing the transformer in either DC or AC mode i came to the conclusion that AC gives better sound with less crackling and a more stable arc, while DC is simpler because the voltage builds much higher and the arc self ignites. I decided to go with AC because of clearer sound.
One of the challenges with this build is to make it possible to trigger the arc automatically, you will notice that i do this by using an insulated metal tool (pliers) in the teaser video. Eventually this will be solved electromechanically by using a servo to move the electrodes close to each other, and then move them apart when the arc has triggered. I will also need to monitor the current of the high voltage in order to re-trigger the arcs if they extinguish for some reason.
See the teaser video below for a short preview.
The high voltage in this design may be lethal depending on how the device is constructed, it may also interfer with RF devices nearby, this project should not be attempted by anyone without basic knowledge about high voltage safety and local RF shielding laws.