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fequency modulation calculations
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bod



Joined: Apr 28, 2009
Posts: 148
Location: Glasgow

PostPosted: Fri Aug 06, 2010 3:57 am    Post subject: fequency modulation calculations
Subject description: Help required for dummies.....
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As far as standard VCO's are concerned its easy enough to implement multiple CV's from pots, ADSR's and LFO's etc with a summing mixer opamp.

But to be honest I know little of what actually happens when you add all these together and into a VCO. Is there any idiots guide anywhere on what is actually happening that I could read? I've found a lot of stuff but there are lots of formulas for what is happening, but its all a little confusing at the moment.

The reason I ask is because of the DCO I'm trying to build. Its simple when you are just controlling the frequency for notes, but when you want to start adding envelope and LFO modulation then I'm kinda lost as to how to code it. hardware is alot easier for me!

Now I presume that when you are setting the frequency with a note, say C4, and an LFO with a depth set to sweep between 2 octaves, then the frequency will sweep between C3 and C5, centred around C4 which is my note value... if the note value was E4, then the frequency would sweep between E3 and E5...

Or have I just completely made that up?
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Sound



Joined: Jun 06, 2006
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PostPosted: Fri Aug 06, 2010 12:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Now I presume that when you are setting the frequency with a note, say C4, and an LFO with a depth set to sweep between 2 octaves, then the frequency will sweep between C3 and C5, centred around C4 which is my note value... if the note value was E4, then the frequency would sweep between E3 and E5...

Yes I think that it is correct as exponential frequency modulation.

The summing exponential converter, just sums all the voltages, Coarse, Fine, Keyboard, LFO, Envelope... whatever you sum there. And then the result is translated to 1V/octave.
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Jack_Hertz



Joined: May 14, 2010
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PostPosted: Fri Aug 06, 2010 1:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

In software, anything goes since you can define the increments anyway you like. Ideally, make it an option to choose to modulate by cents or frequencies so you can do chromatic and microtonal stuff at will.
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