Circuit Snippets

[Jaicen_solo]

Hey guys, does anybody know how the quick & Dirty VCF works??
I'd really like to use it in one of my projects as a really simple low-pass filter, but i'm a bit confused. There doesn't seem to be an envelope detector, so i'm guessing that the CV in needs to vary the voltage to ground, Is this correct??

Also, does anybody have any ideas for filtering square-waves like those generated by the PWM to produce something approaching a saw-tooth??

Thanks,
*j

[jmusser]

I asked the same question awhile back. Look for "Need Explaination For Tim's Quasi Synth". Tim tells how it works on there. If you look a little further down the "Snippets" page, you'll see that Tim's Simple Square Wave Shaper does just exactly what you're asking for, as far as changing a square wave to a saw tooth wave form.

[Jaicen_solo]

Hmm, I can't seem to find anything. I've done a search, and gone through the posts too. Can you give me a little more direction??
Thanks,
*j

[jmusser]

Try http://diystompboxes.com/sboxforum/viewtopic.php?t=28937&highlight=vcf  hopefully that will work. It will be topic 28937

[Jaicen_solo]

Ah ok, I understand how VCF's work, my question is, how do I sweep this particular VCF?
I'm guessing that I can use variable resistance to +V, perhaps using an LDR??