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Coriolis
Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark
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Posted: Thu Nov 23, 2006 4:54 am Post subject:
How to convert MFOS 12 db SVF to 15V operation? Fixed! Subject description: God I'm dumb! But it doesn't oscillate...? |
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This is mentioned in the thread about voltage dividers too:
Has anyone here built Ray's 12 db svf and succesfully converted it to 15V operation? I'm talking about the one without vc res here:
http://www.musicfromouterspace.com/analogsynth/statevariablefilter.html
As far as I can see, it would involve changing the values of a whole bunch of resistors, but exactly which ones, and to what values, is beyond my capabilities to figure out.
I looked at the schem for his other svf to find clues, but they are quite different designs.
Any clues?
C Last edited by Coriolis on Tue Jan 16, 2007 12:10 pm; edited 1 time in total |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Thu Nov 23, 2006 7:10 am Post subject:
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Same answer.
A 7812, a 7912 and 4 caps. _________________ What makes a space ours, is what we put there, and what we do there. |
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Coriolis
Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark
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Posted: Thu Nov 23, 2006 7:16 am Post subject:
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Jeez, you're everywhere!
Yeah, but if I use regs every time I come across a 12v ckt, I won't learn how to convert it will I?
C |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
Audio files: 52
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Posted: Thu Nov 23, 2006 7:23 am Post subject:
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There are heaps of other things which I'm alot more interested in learning. _________________ What makes a space ours, is what we put there, and what we do there. |
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Coriolis
Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark
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Posted: Thu Nov 23, 2006 7:28 am Post subject:
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Yes...priorities, priorities...
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synth_ollie
Joined: Sep 11, 2006 Posts: 149 Location: sweden
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Posted: Thu Nov 23, 2006 7:50 am Post subject:
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on the mfos startpage you can read :
>Do your circuits work
>with +/-15V?
>All of my circuits will work with +/- 15 volts and in all >probability, with no changes.
I´ve built this vcf and I worked fine on +/- 15v as it is
cheers
OLLIE |
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Coriolis
Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark
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Posted: Thu Nov 23, 2006 8:49 am Post subject:
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Really? That's weird, because on mine, the range is way off...
Strange...
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synth_ollie
Joined: Sep 11, 2006 Posts: 149 Location: sweden
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Posted: Thu Nov 23, 2006 3:55 pm Post subject:
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Coriolis wrote: | Really? That's weird, because on mine, the range is way off...
Strange...
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well it was a while ago since I used it, but as I remember there were no problems... but Im sure you can get the range ok by changing some resistor values |
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Coriolis
Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark
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Posted: Sun Jan 14, 2007 1:00 pm Post subject:
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Sorry to dig up this old thread, but I was just looking at the schems for both of Ray's svf designs and wondered:
On his vc res design, which he sells boards for, the frequency pot sits between + and - 12V, with the wiper carrying the cv.
On the other one (the one I'm building), frequency pot sits between + 12v and ground, with the wiper carrying the cv!
What's going on there? I know I said in the first post of this thread, that they were two "very different" designs, but I take that back: apart from the vc res part, they actually look very much the same, except for this frequency pot business. Could this be why running it on +/-15V screws things up?
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Coriolis
Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark
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Posted: Tue Jan 16, 2007 12:18 pm Post subject:
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Well, it's official - I'm a grade-A moron.
I think I've been over that board a dozen times or so, checking for component values, solder bridges, etc. For some reason though, I didn't think to check the trimmer - how about that, instead of a 100R trimmer, I put in a 100K!
Now it works...
Guess there's a lesson in there: To debug a circuit effectively, assume that you have done everything wrong!
Only thing that isn't quite there yet, is that it doesn't self-oscillate at max resonance - which it is supposed to do. Am I right in thinking about reducing the value of R4 (47k at point "Q1" next to the input) to get more feedback?
http://www.musicfromouterspace.com/analogsynth/statevariablefilter.html
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
Audio files: 52
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Posted: Tue Jan 16, 2007 3:27 pm Post subject:
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Not a moron at all!
To accept that there may be a fault in your beautiful new creation, and then go and find said fault, accept it, and own it, and fix it! Now that's the work of genius! _________________ What makes a space ours, is what we put there, and what we do there. |
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synth_ollie
Joined: Sep 11, 2006 Posts: 149 Location: sweden
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Posted: Tue Jan 16, 2007 3:47 pm Post subject:
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mine did not self oscillate either.... |
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