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 Forum index » DIY Hardware and Software » Circuit Bending
VTECH Genius leader - pitch controlled by coil?!
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AnalogLEJ



Joined: Aug 06, 2010
Posts: 3
Location: Hamburg Germany

PostPosted: Fri Aug 06, 2010 3:53 am    Post subject: VTECH Genius leader - pitch controlled by coil?!
Subject description: cb questions for pitch mod
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Hi There, I never did CB before but started with a project of modding a VTECH Genius leader Color Child Computer. I am no electronic freak but know some basics and generally just noodle around Wink Maybe a bit too much for a first project - but too late now, I already did too much to stop again Wink

I already found some rockin' bends by noodling around. Those are are all shortage-bends like sample hold, stutter, etc. I have not found one yet which is cool and controllable by a potentiometer. So I started to try to find a pitch mod.

However, I got stuck with trying to bend the pitch of this thing. I already found that they use a variable coil that can be used for adjusting the pitch. It seems that the frequency of this coil is also driving some sort of CPU clock as the whole user interface gets faster if I change the frequency. So I am not very sure if I am doing the right thing or if I should better search another way of pitch-shifting the sound. However, its way to inflexible - I need a screwdriver to change it and it only changes within a very low range.

One thing that was very cool is when I use a magnet to noodle around the coil with it - thats what I need, but not by using a magnet but a Knob!

So first I removed the coil and replaced it with some wires for better testing. I then tested different quartz crystal oscillators with different frequencies and can so modify the pitch quite well. But I want that as a pot and not only switch between different static frequencies.


The only thing I can currently imagine is to get some digital oscillator IC where I can somehow control the frequency. But I dunno if this needs to provide a square or a sine or a tri or whatever. I even dunno if there is such an IC where I can use a potentiometer to control the frequency of the output signal. As said, I am not very good in electronics.

I found something that might be working which is called LTC1799CS5

But thats a SMD IC, I can never ever solder that somewhere without breaking it, I am a noob Wink


Any suggestions? Anyone did a complex VTECH Toy yet? This one seems to be very complex. I attached a pic of the mainboard.[/img]


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electri-fire



Joined: Jul 26, 2006
Posts: 535
Location: breda nl
Audio files: 4
G2 patch files: 4

PostPosted: Fri Aug 06, 2010 4:54 am    Post subject: Re: VTECH Genius leader - pitch controlled by coil?!
Subject description: cb questions for pitch mod
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AnalogLEJ wrote:

I found something that might be working which is called LTC1799CS5

But thats a SMD IC, I can never ever solder that somewhere without breaking it, I am a noob Wink


I had some of those LTC1799's as free samples. When they came initially I thought the bags were empty. They are minute. totally unfit for DIY.

You can get them on a little circuitboard here: http://www.getlofi.com/?page_id=1302

(they've reduced the price, I think the used to be $25.- in the past, now $15.- with knob, $10,- without knob)

I've used the 74LS624 - 74LS629 clocks for some bends. Works great, are DIL, are voltage controlled. Some have a voltage controlled Range pin that I used for external control. Warning: they work on 5V maximum!

I have a couple left, but I've seen them for $3,- or something.

Here's what got me into them:
http://www.xs4all.nl/~samzen/synth/circuits.html

I used just one pot as a voltage devider for pitch, and had the range pin to 5V or switched to external CV.


74LS626N - VOLTAGE-CONTROLLED OSCILLATORS.pdf
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electri-fire



Joined: Jul 26, 2006
Posts: 535
Location: breda nl
Audio files: 4
G2 patch files: 4

PostPosted: Fri Aug 06, 2010 5:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh, readability enhancement.


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AnalogLEJ



Joined: Aug 06, 2010
Posts: 3
Location: Hamburg Germany

PostPosted: Fri Aug 06, 2010 7:05 am    Post subject: Reply with quote  Mark this post and the followings unread

wicked! thank you very much. I think I'll go for the getlofi board. I heard of that site before (especially from DIY YT videos) but never ordered something there. I wonder why I did not recognize them having this board. Looks like they deliver internationally, so I'll take the chance and get some other of their cool DIY stuff like the 555lfo + sequencer as well
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