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 Forum index » DIY Hardware and Software
Saw Wave Folder
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Ricko



Joined: Dec 25, 2007
Posts: 230
Location: Sydney, Australia
Audio files: 27

PostPosted: Sat Aug 18, 2018 4:38 am    Post subject: Saw Wave Folder Reply with quote  Mark this post and the followings unread

Here is a circuit idea. Wavefolders are now pretty well-known kind of waveshaper. They are often made from a chain of circuits that fold the wave back on itself, after it has reached a certain level. The effect can be like a sweep up harmonics or hard sync. It tends to work best for sine/triangle waves, not so good with sawtooth (too much variation in strength of harmonics) and pulse (not much effect).

So I wanted to make one for sawtooths. I am not sure whether the idea is really mine: probably not. It can be built with a quad comparator, & 3 dual op-amps, all vanilla components.

This version here does not use a folder, it uses a chain of fairly standard sawtooth doublers: once the sawtooth is over a threshold, each subtracts the PP amount. So increasing the level causes more folds: first the first doubler, then the second and so on.

So this circuit has four doublers that act to allow sweeping up to 5 x the frequency. You can see example waveshapes in the image below. The green is the input, the purple is the output.

As a bonus, there is a kind of pulse-width option too. It is an offset, so it could be a CV quite readily.


SAWWAVEFOLDER.JPG
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SAWWAVEFOLDER.JPG



Last edited by Ricko on Wed Aug 22, 2018 10:52 am; edited 3 times in total
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vladosh



Joined: Aug 02, 2010
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PostPosted: Sun Aug 19, 2018 10:20 am    Post subject: Reply with quote  Mark this post and the followings unread

this looks interesting i built similar but fixed version from electronotes ,second thought this idea with stages can be useful musically ,thanks for sharing
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Ricko



Joined: Dec 25, 2007
Posts: 230
Location: Sydney, Australia
Audio files: 27

PostPosted: Wed Aug 22, 2018 3:25 am    Post subject: Reply with quote  Mark this post and the followings unread

vladosh wrote:
this looks interesting i built similar but fixed version from electronotes ,second thought this idea with stages can be useful musically ,thanks for sharing


Thanks.

Yes, to be clear, this isnt four fixed outputs, it is an output that varies from saw to quintuple saw as you turn the fold pot.

And if you replaced the fold pot with some vca thing, it would be under voltage control. (The width pot is a bias effect no different from adding a cv offset to the input saw, like you can do with normal wave multipluers.)
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Ricko



Joined: Dec 25, 2007
Posts: 230
Location: Sydney, Australia
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PostPosted: Fri Jun 14, 2019 10:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

VIDEO + AUDIO: I put up an example of the prototype PCB version of these.

https://www.youtube.com/watch?v=mbRE_3tlnFI

I am taking another iteration of the PCB: the plan is to bring it out as a module called fricko Rasp maybe next month, if it is OK.

Last edited by Ricko on Sat Jun 15, 2019 10:19 pm; edited 1 time in total
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Ricko



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Posts: 230
Location: Sydney, Australia
Audio files: 27

PostPosted: Sat Jun 15, 2019 10:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

AUDIO: And here is a sample audio file showing one of the kinds of sound, in this case right on the edge of a transition so that sometimes you get a little second thin pulse that shows up as sizzle sound. Unfortunately is is only 16kHz sample, so you don't get the top octave of sizzle, but I thought people might be interested.


sizzle.wav
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"sizzle" sound of saw wave folder (fricko Rasp prototype) with slight modulation by LFO.

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 Filename:  sizzle.wav
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