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Best schematic for modulation with piano?

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LAN_403

Killa-X

Sun Jan 03 2010, 08:36AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Apparently there's a looooooot of methods on google, and no one seems to post their schematics, only Xenosonic. What is a good, fairly easy to build audio modulator for a SSTC? Awhile back i tryed a LM358, and had audio in, and it outputs that same audio, in a square wave form. Duty wasn't controllable, and it didnt play on the SSTC good, very crappy. So I'm asking what schematic i can use to be able to take my piano, have it be audio modulated, and fiber cabled to a DRSSTC. I figured setting my piano to a sound with square waveforms, Such as 'Square LED', would make it easier to create a nice sound. But I never manage to get ahold of something that would allow me to do it right.

I tryed a 555, but it never worked, sure on speaker i heard audio, but on the SSTC, nothing really. When i turn the frequency down, it was getting better, but there was a constant bleep, due to the frequency being under 20khz range :(

Thanks you!

Mads Barnkob

Sun Jan 03 2010, 09:16AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Reachings modulator is easy to build and works fine for a SSTC, its the one I have used for my SSTC.

Schematics can be found somewhere on ctc-labs.de or on my website under the SSTC II.

Killa-X

Sun Jan 03 2010, 10:06AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Mads Barnkob wrote ...

Reachings modulator is easy to build and works fine for a SSTC, its the one I have used for my SSTC.

Schematics can be found somewhere on ctc-labs.de or on my website under the SSTC II.

Ah, Thank you. Would a LM358 or LM386 work in replacement of taht lm741? Looks like they're all the same...until i get my fiber cable, ill have to midi test on a old mp3 player...wont risk piano without that fiber cable!

Dr. Dark Current

Sun Jan 03 2010, 11:07AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

A simple "full-spectrum" audio modulation for a SSTC is to use the VCO of the 4046 chip, tune it a bit above resonance, and AC-couple your audio signal into the VCO input.

Myke

Sun Jan 03 2010, 05:03PM

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

Killa-X wrote ...

Ah, Thank you. Would a LM358 or LM386 work in replacement of taht lm741? Looks like they're all the same...

No. You can't use them interchangeably. Both the LM358 and the LM741 are op-amps but the LM358 can work off a single supply at a lower voltage than the LM741 which needs a split supply at a higher voltage. There are ways to get around the dual supply need of the LM741 but it's a good idea to use the part specified in the original design. The LM386 is not an op-amp.
Here are the datasheets for each op-amp/audio amp
LM358

LM386

LM741

Killa-X

Sun Jan 03 2010, 05:09PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Dr. Kilovolt wrote ...

A simple "full-spectrum" audio modulation for a SSTC is to use the VCO of the 4046 chip, tune it a bit above resonance, and AC-couple your audio signal into the VCO input.

Wouldnt that mean if I change the topload, i might have to fix the tuning on the chip? Guess id get a high percision pot. My coil, no topload is 350khz.

R1 = 9K | R2 = 3K | Cap is 10pf, would come out to a typical 367khz with 2.5Vtun, if that's the case.

Dr. Dark Current

Sun Jan 03 2010, 05:56PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Yes, you'd need to change the tuning with a different topload. This can be done by using a trimpot instead of a fixed resistor for R2 (from pin 12)

Killa-X

Sun Jan 03 2010, 11:58PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

I see that could be the reason you dont use LM385 :)

For fun, after 2:00 is just some messing with my tesla coil a few days ago, not with audio modulation however. Also, when i had audio to the 10uF capacitor, then resistor, to pin 3, nothing. So i put direct audio to pin 3, and heard it. caps / resistor values are correct, but my 100ohm resistor, that goes from +V to the transistor, closest to the 555, gets hot. and its a 10W resistor.

(breadboarded the audio modulation area)

uzzors2k

Sun Jan 10 2010, 05:49PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

You should look into MIDI interrupters if you just want to play a piano on your Tesla coil. Though you'll only be able to play square waves it still sounds pretty good. No modification of the Tesla coil is needed, provided it has an interrupter input.

Killa-X

Mon Jan 11 2010, 05:09AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Well. I was able to do a fiber cable from my computer. I used audio to a IR. Then had a IR switch (NPN) to send 9v into the uccs. With FL tudios I can hear nearly every instrument. Square. Saw. Triangle all sound good. Instruments that do a wahwah effect fully work. All together I get very clear quality. The one from the Sawyer instrument...FG prophet... Sounds exaxct. My YouTube video uses it. Just note my cam didn't capture the equality. But it sounds the same exact way it does on my computer. Nice and clean. Other instruments that dot use square work too. Must any midi works.

actually, cool how the output is the same size as it is when I use a normal interrupter. Same sized when audio modulated. In the video, I ran it on low power. 2" output. Was still loud. Max I can do so far is 8". Tomorrow I'll test modulation at 5"

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