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Simple Audio modulated SSTC

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williamn

Fri Apr 28 2006, 05:02AM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
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Posts: 149

Here is a neat little SSTC I built last night. I had a few left over mosfets from my brick drivers. Its just a 555 astable set to 50% dutycycle and a freq range of 700-800Khz, audio input on pin 5 (Control V). The secondary coil measures 2.5" diameter, 8" long wound with 31AWG magnet wire. A measured Fres of 775Khz. Gate drive is handled by the UCC37322/21 chips. It was tricky getting these drivers to handle the high freq, they do get warm. I added a heatsink to them along with a bunch of thermal goop, they dont get too hot now after long runs. Vin to the half-bridge is fullwave rectified and filtered 40VDC. I wanted to make the whole setup extrabeefy so I can run it or long periods. The longest run so far is 10 minutes and everything seems fine. This coil is still in its lash up phase so its a work in progress. I have lashed up a few of these 555 audimod coils in the past and I want to make this a permanent coil.

video of coil running. 5.5MB sorry!

pic

Dr. Drone

Fri Apr 28 2006, 06:25AM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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williamn

Fri Apr 28 2006, 02:59PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

Thanks CR! For the last version of this circuit I put together I used a 450Khz secondary and the audio did not sound as good as with this one. Sound quality is pretty decent with this little coil. Now I think I am going to build a ClassE 3-4mhz coil and audio modulate it for even better quality sound.

Dr. Drone

Fri Apr 28 2006, 04:01PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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Part Scavenger

Fri Apr 28 2006, 05:14PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Ray Charles would be proud.

That's cool Will!

Avalanche

Fri Apr 28 2006, 09:02PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Very good!

The only problem I always have with AF modulated coils is that the MOSFETs heat very badly due to the hard switching, and eventually burn out because of this. Was that 10 minute run with the audio on? How do the FETs run when the audio is on? Today I've started building a very similar coil to yours, a halfbridge but PLL driver, probably about the same size too. I'll try the audio modulation and see what happens. I find that the ICL7667 gate driver chips work much better with higher frequency coils, as they are high speed drivers, but it looks like I'll have to use UCCs as well because i'm out of the others.

williamn

Fri Apr 28 2006, 11:28PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
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Posts: 149

UCCs are pretty fast. I used the TC4422/21 chips at first and they just got smokin hot. I too have built a PLL SSTC and audio modulated it, but it was a lower freq coil and sound quality suffered. HF PLL might be the way to go. The 10 minute run was with audio on, and the fets stay fairly cool, I am not pumping a ton of power here, its hooked up to my 20A variac and current consumption is about 2A, so 80watts total. Audiomoding is quite cool. Please post youre results!
Will

coaster_chris

Mon May 15 2006, 12:26PM

Registered Member #359 Joined: Sat Apr 01 2006, 09:27AM
Location: Utrecht, The Netherlands
Posts: 16

Sweet dude!!

It's just such an amazing effect... Having sound comming of the streamers!

I'm planning on buildiung an audio modulated SSTC too, hopefully done by christmas... 2008!

I still have a lot of reading to do about the solid state coils, but... I'll get there!

Keep up the good work willimn

Chris

HV Enthusiast

Mon May 15 2006, 01:18PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Chris,

I have a lot of information on the audio modulated coils I built including the stereo Plasmasonic systems on my website here:

http://www.easternvoltageresearch.com/design_resource.htm

There are schematics, parts lists, artwork files, and a presentation or two on the audio modulated stuff. You should find it helpful.

Dan

coaster_chris

Mon May 15 2006, 01:51PM

Registered Member #359 Joined: Sat Apr 01 2006, 09:27AM
Location: Utrecht, The Netherlands
Posts: 16

@Daniel

But ofcourse I've checked out your website allready!

It has a lot of helpfull information indeed. Coming acros a movie of the plasmasonic and some other audio modulated coils on a website ( Link to movie ) actualy gave me the idea for a new project, after finishing my SGTC.
(I'll post soms specs and pics of my SGTC if I have some time. The only pics I have at the moment are realy poor, telephonecam, quality.)

BTW. The soundquality of your plasmasonic is actualy pretty darn clear!

Tnx, anyhow...

Chris

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