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My 4Mhz amplitude modulated audio sstc

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LAN_403

Firefox

Wed May 07 2008, 08:36PM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

Wow, that is awesome! Could you add some values to the schematic? This looks exceedingly simple, and I would like to build one like it to show off in physics class.

Reaching

Wed May 07 2008, 09:13PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

yeah, its pretty simple. next week or so i can get the shematics finished. the shematics shown above do not represent the whole circuit. its a bit more complex than that but compared to other circuits its really simple.

Reaching

Fri May 09 2008, 10:30AM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

New Video

I build a new secondary and tuned the class e circuit.i nearly doubled the power and now i think its fine :)

Dago

Fri May 09 2008, 11:23AM

Registered Member #538 Joined: Sun Feb 18 2007, 08:33PM
Location: Finland
Posts: 181

Reaching wrote ...

New Video

I build a new secondary and tuned the class e circuit.i nearly doubled the power and now i think its fine :)

Looks and sounds great, looking forward for more information about it. Does the interference (the sizzle or something that appears in the chorus of the first song) come from the coil or does the camera/microphone just get interference from the coil?

Reaching

Fri May 09 2008, 11:44AM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

this noise that appears from time to time is due to the disortion of the microphone. sorry, but i have no better cam for recording. in reality it sounds like some of this ultra high fidelity speakers.

Dr. H.

Fri May 09 2008, 12:43PM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Awesome Reaching. It will be very cool when you box it

Cheers Huben

WaveRider

Fri May 09 2008, 01:55PM

Registered Member #29 Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500

Very nice! The transformer modulation scheme in the drain circuit is a good old-fashioned AM transmitter method for very linear modulation. The drawback is that the audio amplifier must be powerful enough to provide the depth of modulation you need...up to 50% of the total AM signal power for 100% modulation as well as a big enough transformer to avoid saturation (altho' air-gapping the core reduces this effect)...

If you are going to the trouble to design a regulated DC powersupply, why not design a system where you apply the modulation to the regulator feedback. In effect, using the regulator as an audio amplifier that also handily provides DC bias? Then you would only need a small audio signal...and the feedback would help linearity too!

Also, with deep modulation, you get power-dependent detuning of the tesla coil as the discharge size/temperature is modulated. This introduces non-linearities in the acoustic generation. For this reason, a tracking oscillator using a power oscillator or PLL circuit are recommended.. (in fact, most plasma tweeters I have seen use vacuum-tube power oscillators that are "self-tuning"..)

Great work!!!!!

GeordieBoy

Fri May 09 2008, 03:46PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

If you are going to the trouble to design a regulated DC powersupply, why not design a system where you apply the modulation to the regulator feedback. In effect, using the regulator as an audio amplifier that also handily provides DC bias?

Yeah, that is basically what the Class H modulator does. Except it makes use of a split rail supply so that dissipation in the modulator is minimised around the quiescent operating point (normal carrier level.)

By the way, has anyone investigated using Carrier Level Control (DCC) on an audio-modulated Tesla Coil? It would seem like a good way to reduce power draw, minimise corona hiss during quiet passages, and maximise the peak audio volume achieveable with a given set of power semis.

-Richie,

Reaching

Sun Jun 15 2008, 10:13AM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

ive been working on this project for weeks now and made a board, which includes the whole circuit.

its fully analog, without an ic or something. there is a crystal oscillator with 4 mhz for the drive signal. amplified by a simple bc546 transistor and a push pull stage of bd139/140, then fed to a gdt to the class e stage.

the audiosignal is amplified by another simple bc546 with emitter current feedback to provide simple adjustment. a dc bias pot with a smal cap in parallel is for adjusting the dc bias of the linear regulator. you adjust this pot for around 30 to 35v output. the amplifier stage is adjusted to provide around 20-30% modulation of the mosfet gate.

both mosfets are cheap irf630, and all the other parts are easily availiable too. all you need is to plug it in and enjoy :) a transformer with 30V AC and 3-4A current is recommned. the ac voltage is rectified on board and smoothed with 13200ÂµF 50V of capacity.

Myke

Sun Jun 15 2008, 05:34PM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Looks very cool. Nice work.

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