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Old 29th Jun 2018, 12:54 pm   #55
Al (astral highway)
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Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
Default Re: Bach with sparks!

Quote:
Originally Posted by Viewmaster View Post
The modulator I am making will use midi files or a keyboard for the tesla. As I understand it the o/p is sq wave at 5v ( again not enough to directly turn my mosfet in cathode on/off)
Hey Albert... you could put a MOSFET gate driver chip in there to improve gate drive. IXDD414CI is perfect and I've used it up to 4MHz. If your other plan doesn't do what you want, I can give you more deets later down the line.

Quote:
... as I understand it with musical teslas, one can do one of two things.

1. Modulate a continuous plasma flame with the actual music (non sq wave). The result being that awful tinny tiny sound very severely lacking in bass.

2. Modulate a non flame plasma system where square waves at the musical frequency turn a spark discharge on/off to produce a note.
I see what you mean, only I've only ever seen (2) applied to solid state coils. These are 'hard switched', by which I mean, simplifying a bit, that the switching transistors are really close to being like a mechanical switch, either on or off.

So the square wave is relevant and essential here because it has vertical edge and also because it biases the gates off really quickly. They are usually in pairs or a quad of two pairs. If one of the pair wasn't off when the other one was switched on, it would be up in smoke in a few microseconds.

I have never heard of digitised audio files being used to drive a valve Tesla coil on the grounds of musical fidelity. It doesn't make sense, as square waves are full of spurious harmonics that aren't in the original. Also, you will have sounds that originally dwelled/decayed slowly being chopped harshly, and to me, that sounds like a robot playing a keyboard.

Quote:
Have I got this all wrong? It's what I have gathered searching the net for info.
I do think there may be some confusion there.

However, when you describe 1) above as tinny and lacking in bass, that's also true. So you can choose that, or your in my opinion robotic-sounding square wave, which as I say I haven't previously seen married with valve Tesla coils because the over-engineering involved may not be worth it in sound quality terms.

But no harm done if you experiment away, only a caution again with audio signals coming from a PC or a mobile - isolation, isolation, isolation!
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