FEELER: Plasma Speaker Kits

Meatball · Mar 28, 2013

Huh. Perhaps I missed the buzz in the original videos?

Sigurthr · Mar 28, 2013

Towards the upper end of human hearing range 1kHz can represent almost 9dB difference in perceived volume. A 1kHz shift at ~16kHz is well within 10% variance in component values within tolerances. I'm not sure what chip you're using for the PWM, but raising the frequency is usually just changing one resistor or capacitor.

Things · Mar 28, 2013

It uses a CD4046 PLL, and I agree that it is very likely to be the PWM you're hearing, I think the culprit may actually be excessive trace lengths.

The original video I believe is the kit Fiddy bought, ans is basing his kit around. The original has a much smaller PCB than the prototypes he made, however I believe component values are the same.

I did a frequency analysis of the whine last night, and it has fundamentals at 775Hz, 1549Hz, 2323Hz, 3882Hz and some other inaudible frequencies. So yeah, seems highly likely it's PWM related, as they're all harmonically related.

Sigurthr · Mar 28, 2013

Well, there is not a whole lot you can do since you're using a 4046PLL as it is both the main oscillator and the PWM chip in one. It uses your f0 as the pwm carrier. How loud is it actually in person?

Things · Mar 28, 2013

Pretty hilarious how this thing broadcasts smack bang in the middle of the AM radio band. I can actually tune a plain old AM radio into the coil from out in the street, and the quality is better than the real AM stations

Fiddy · Mar 28, 2013

Sigurthr said:
Well, there is not a whole lot you can do since you're using a 4046PLL as it is both the main oscillator and the PWM chip in one. It uses your f0 as the pwm carrier. How loud is it actually in person?

interesting, its enough to piss me off, it is noticeable when playing audio through the arc and really obvious when there's no audio playing.

Things · Mar 28, 2013

Yeah, though there is clearly a way to fix it, cos it doesn't happen on the original coil

I agree with Fiddy though, it's not deafening, but it's kind of annoyingly noticeable.

If you do actually have all the exact same component values, and having your prototype coil next to it and it still not doing it, really it can only be put down to the PCB layout.

I'd reckon the issue will disappear with the new smaller board

But I've got a few more ideas to try first.

Sigurthr · Mar 28, 2013

Things said:
Pretty hilarious how this thing broadcasts smack bang in the middle of the AM radio band. I can actually tune a plain old AM radio into the coil from out in the street, and the quality is better than the real AM stations

That is actually really freaking awesome, haha. Just be careful no radio snoopers catch on, here in the US big fines and confiscation comes with unlicensed broadcasting. All my coils are in between registered radio bands.

Things · Mar 28, 2013

Yeah haha, luckily I live in a smaller city, along with a tin roof on my house, in a valley. And a tesla coil doesn't really make an optimal antenna, so it really doesn't transmit far. It is pretty awesome being able to listen in to the coil on a radio though, but that damn whine becomes even more obvious!

I almost had a visit from the RF cops once, while playing with FM transmitters a few years ago

Sigurthr · Mar 28, 2013

The TC itself doesn't make a good antenna, no, but the power lines it capacitively couples to do. It isn't the same as having real radio equipment as far as actual transmitted power or field strength, but it is enough to still in trouble. I think you'd be fine with your plasma speakers though, it doesn't look to be above 300W or so. It is another story if my 2kW coil were to be on a radio band, heh. If even 5% of it were to get radiated effectively I would have the FCC on my butt.

I just built up a 4046PLL driver btw. I tried one once before I had a scope and it was a failure, but I've come a long way in the years since then so I'm ready to give it another shot. Just waiting on the timing cap in the mail and I'll be ready for first light.

rdyno · Mar 28, 2013

I am interested I am from aus so postage will be simple well...... I'm not going into the postage here lol, how much for two?

Meatball · Apr 3, 2013

Any updates on this?

Fiddy · Apr 3, 2013

rdyno said:
I am interested I am from aus so postage will be simple well...... I'm not going into the postage here lol, how much for two?

depends what you want in the kit.

Meatball said:
Any updates on this?

Ive done a lot of modifications to the board that will help get rid of this hum in the plasma, will order some new prototype boards soon

Also working on a SSTC design that i may release in a kit like this also

Meatball · Apr 3, 2013

Thanks for the update Fiddy, I really looking forward to seeing what you've made!

dakyone · Apr 3, 2013

Also eagerly awaiting developments. :can:

bassa · Apr 4, 2013

Things said:
Thanks, took quite a bit of trial and error to get the casing right.

Also when I first put it together in the case, it wouldn't work properly, no breakout at all. Found out that you need to keep the primary wires away from the antenna apparently!

I need a wider range of various gas-filled tubes to play with

Hallo.
I am new at the forum. I howlp I don't ask any stupid questions...

I managed to do a plasma speaker, but I wanted to be with Tesla coil.
My power is DC 12V, but the coil does not come niches. If you can give me some advice or tell me something about your schedule that you have made.

Plasma speker - YouTube

Sorry if my English if I do not understand very well.

FEELER: Plasma Speaker Kits

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