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 Forum index » DIY Hardware and Software » Circuit Bending
Help pitch bend
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vihreä



Joined: Mar 26, 2015
Posts: 5
Location: finland

PostPosted: Thu Mar 26, 2015 12:51 pm    Post subject: Help pitch bend Reply with quote  Mark this post and the followings unread

I got superb sound ek908 called synth. Trying to get pitch bend. Can anyone see where the potentiometer should be soldered to? Other bend tips also welcome Smile Thanks in advance!

Here's a photo of the circuit:

https://dl.dropboxusercontent.com/u/2738029/IMG_0610.JPG


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vihreä



Joined: Mar 26, 2015
Posts: 5
Location: finland

PostPosted: Thu Mar 26, 2015 10:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

the chip is this:

http://www.pselectronic.cz/pdf/1120/1120874.pdf

The manual says it has
On-chip crystal oscillator: 3.58MHz

Does it mean it can't be pitch bent?

Could i somehow limit the voltage to effect as a pitch bend?

Thanks for any help!

EDIT: And there is two pitch buttons on the synth, other lowers and other makes it higher, I just want to control it with potentiometer. Transpose buttons i mean.
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Fri Mar 27, 2015 8:10 am    Post subject: Reply with quote  Mark this post and the followings unread

welcome

when I read On-chip crystal oscillator I thought it would be one inside the chip, but a look at the schematic showed me
that this isn't the case. So yes you should be able to control the pitch. To do this you will have to take out the crystal
(marked in the photo below) and use an adjustable high speed oscillator instead connected to pin 24.
For circuit bending the LTC1799 is often used and you can find some more info about that here.

You could also use a 74HC4046 which is probably easier to find and cheaper and because the oscillator is a VCO
you can control it with something else aswell.


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vihreä



Joined: Mar 26, 2015
Posts: 5
Location: finland

PostPosted: Fri Mar 27, 2015 6:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

yey, im happy to know it can be circuit bent.

is this the right part:

http://www.ebay.com/itm/2x-74HC4046-744046-Phase-Locked-Loop-with-VCO-CMOS-Verrouillage-De-Phase-DIP-16-/151564174171?pt=LH_DefaultDomain_71&hash=item2349edc35b

Can I make some other bends with that also?
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PHOBoS



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PostPosted: Fri Mar 27, 2015 6:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

yes that is the correct part. as for other bends with it I can't really tell yet.

Maybe you could use one as an oscillator at an audio frequency and mix it with the output of the keyboard.
If that output signal is a squarewave, which is could be, than you could mix it using the XOR gate of one of those chips.
This will give you a somewhat metallic (ringmod) sound. Or you could use the output of the keyboard to control the frequency of it.

It depends a bit on how much experience you have with electronics.

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vihreä



Joined: Mar 26, 2015
Posts: 5
Location: finland

PostPosted: Sat Mar 28, 2015 12:35 am    Post subject: Reply with quote  Mark this post and the followings unread

im a rookie on electronics. but i learn fast.

so if I want to make the pitch bend and try some other bends too I should get more than one of those chips?

do you know how to install it to make the pitch mod? i have few potentiometers already, do i need some other parts too? im looking to mod the synth for very cheap.

thanks for all the help
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PHOBoS



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PostPosted: Tue Mar 31, 2015 8:30 am    Post subject: Reply with quote  Mark this post and the followings unread

I'd focus on the pitchbend first but get at least 2 chips in case you fry one in the process Wink
You also need a small capacitor, not sure of the value yet would have to calculate that, but probably something in the pF range.
And maybe a resistor or two to make the control a bit nicer but it's not necesarry. Then you'll need something to mount
the chip on like a piece of perfboard and I would advice you to use a socket for it.

do you know how to read circuit diagrams ?

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vihreä



Joined: Mar 26, 2015
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PostPosted: Tue Mar 31, 2015 8:34 am    Post subject: Reply with quote  Mark this post and the followings unread

yea i think i already broke the synth. so i guess i dont need help anymore. it just flashes the digit screen and turns off Sad couple of times it stayed on but no sound came out.
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PHOBoS



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PostPosted: Sat Apr 04, 2015 6:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

that's too bad but a risk of circuit bending, especially if you randomly connect things together to find nice bends.
And even if you get something working they sometimes just stop after a while. I had some devices do that out of the blue.

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