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 Forum index » DIY Hardware and Software
4069 State Variable Filter (no VCF)
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synthmonger



Joined: Nov 16, 2006
Posts: 578
Location: flada
Audio files: 3
PostPosted: Sat Nov 01, 2008 8:59 am    Post subject: Reply with quote  Mark this post and the followings unread
ScottG wrote:
Can you tell us more about the conditions of this setup? I'm unsure as to how synch applies to a filter?? I get synching an oscillator, but not a filter.

Also, can you post your final schematic? (assuming this is the final design)...

Thanks for the demo. Interesting, wierd sounds.


This is taken from the video info:

"In the video I have a single oscillator running through the filter while another oscillator is syncing the vcovr which is controlling the filter frequency. The resonance is set at max and is self-oscillating, which is very unusual since state variable filters are not supposed to self-oscillate. I am just adjusting the frequency knobs and showing the different audio outputs. Not much to it."


I haven't built the CGS switched capacitor filter but I assume it's sync feature effects his filter the same way it effects mine.


I'll try to post the schematic soon. I'm busy trying to finish things for an upcoming show. I might post them as late as mid november.

In the mean time you can check out this vcovr schematic. You should really give it a shot, I'd like to hear your thoughts on it.

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StephenGiles



Joined: Apr 17, 2006
Posts: 507
Location: England
PostPosted: Sat Nov 01, 2008 3:58 pm    Post subject: Reply with quote  Mark this post and the followings unread
I suppose that you have seen this?
http://bornagin.net/zeroboard/data/board/getFile2.pdf
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synthmonger



Joined: Nov 16, 2006
Posts: 578
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PostPosted: Sat Nov 01, 2008 4:39 pm    Post subject: Reply with quote  Mark this post and the followings unread
No I haven't actually.
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StephenGiles



Joined: Apr 17, 2006
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Location: England
PostPosted: Sun Nov 02, 2008 4:04 am    Post subject: Reply with quote  Mark this post and the followings unread
synthmonger wrote:
No I haven't actually.


I just wondered if it might be of help. Funnily enough, I breadboarded it a few years back and not having any 4069s, I used 4049s with appropriate pin changes and it worked very well.
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synthmonger



Joined: Nov 16, 2006
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PostPosted: Sun Nov 02, 2008 5:06 am    Post subject: Reply with quote  Mark this post and the followings unread
Did you notice a difference between the two? I've only used a 4069 in place of a 4049 for a guitar tube like distortion pedal and noticed a change in tone. I think the 4069 distortion was a bit crunchier. I'm pretty sure it was craig andertons from his FX book.
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StephenGiles



Joined: Apr 17, 2006
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Location: England
PostPosted: Sun Nov 02, 2008 9:56 am    Post subject: Reply with quote  Mark this post and the followings unread
I tried to find a couple of sound samples I made at the time, but they must have been deleted. One thing I did do was to have 2 filters in parallel, each using different caps, which gave a thicker fillter sound.
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synthmonger



Joined: Nov 16, 2006
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PostPosted: Sun Nov 02, 2008 10:32 am    Post subject: Reply with quote  Mark this post and the followings unread
StephenGiles wrote:
One thing I did do was to have 2 filters in parallel, each using different caps, which gave a thicker filter sound.


I was thinking of doing this too or at least make it an option since there is a whole half of a chip available, but I like using the extra gates for that fun distortion. I'm thinking 3 different kinds of distortion -OD, and two kinds of clipping per gate.
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widdly



Joined: Jun 25, 2007
Posts: 268
Location: singapore
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PostPosted: Mon Nov 03, 2008 7:42 pm    Post subject: Reply with quote  Mark this post and the followings unread
Interesting. Is the 100k offset a trimmer?

I might try replacing the 4016 in your VC resistor circuit with an LF398 to make a VC sample rate reducer.

Have you tried your vc resistor for a voltage controlled glide?

It would probably work nicely for a switched capacitance filter too (http://www.cgs.synth.net/modules/pic/schem_cgs57_bintic.gif)
Last edited by widdly on Thu Aug 05, 2010 10:05 pm; edited 1 time in total
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synthmonger



Joined: Nov 16, 2006
Posts: 578
Location: flada
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PostPosted: Tue Nov 04, 2008 4:34 am    Post subject: Reply with quote  Mark this post and the followings unread
widdly wrote:
Interesting. Is the 100k offset a trimmer?

I might try replacing the 4016 in your VC resistor circuit with an LF398 to make a VC sample rate reducer.

Have you tried your vc resistor for a voltage controlled glide?

It would probably work nicely for a switched capacitance filter too (http://www.cgs.synth.net/modules/pic/schem_cgs57_bintic.gif)


I tried my vco in Bugbrands VC rate reducer and it worked better, plus less parts, sync, expo control etc etc.

Yeah it works well in a VC glide too. As well as EG's and well just about everything.

One thing to note is the linear method adds some distortion that is noticeable in non signal generating schematics. Stick with the 12v/-12v expo for now until I can get the 9V version under expo control.

I use them for my SVF switched capacitor filter.
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synthmonger



Joined: Nov 16, 2006
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PostPosted: Sun Nov 09, 2008 9:40 pm    Post subject: Reply with quote  Mark this post and the followings unread
Quick thought. If the caps were replaced with resistors would it act as a vca?
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