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Registered Member #3989
Joined: Thu Jul 07 2011, 05:10PM
Location: In a van down by the river.
Posts: 52
There is a picture of a plasma speaker on wiki with a vacuum tube. http://en.wikipedia.org/wiki/Plasma_speaker Is the device an audio amplifier and instead of the output transformer being step down type to drive a speaker, a step up kind to generate enough volts to make that corona? I am trying to imagine how it might work. Also my first post here, I think this is a wonderful forum! ~Austin
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hello, the device on the picure is a so called "plasma tweeter" - basically it's a very high frequency (tens of MHz) vacuum tube class-C oscillator, which has its power modulated with music. The modulation on these is usually through the screen grid or cathode.
Registered Member #3989
Joined: Thu Jul 07 2011, 05:10PM
Location: In a van down by the river.
Posts: 52
Dr. Kilovolt wrote ...
Hello, the device on the picure is a so called "plasma tweeter" - basically it's a very high frequency (tens of MHz) vacuum tube class-C oscillator, which has its power modulated with music. The modulation on these is usually through the screen grid or cathode.
Thank you for the reply.
I am not sure I understand. It creates sparks at such a high frequency that we cannot hear them individually and then makes some of them stronger based on the peaks of the music signal waveform. Is that right? If so, then is that the equivalent of amplitude modulation like used in am radio with the carrier wave that stays the same frequency?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Yes, it's amplitude modulated. The running frequency is way above audible range. At such frequency, the output of the coil is a flame instead of the purple sparks at lower frequencies. The power of the flame is modulated, and as it is a hot plasma, it expands and contracts air around it, producing sound waves.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
I feel i should also add that you may see some websites talking about how good the audio quality can be. The flame has virtually no mass, so it can grow or shrink much faster than a speaker with much more mass can move in and out.
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vacuum tube plasma speaker
