hi guys,
im currently building an envelope controlled filter, can someone explain to me the theory behind them and how they work (or point me to a good article)
thanks :D
read the "technology of envelope controlled filters" by mark hammer over at geofex.
http://www.geofex.com
There is also a very good article in Device 1 (I think) also posted on Mark Hammer's site, part of the AMS 100 series which explains the problems in extracting a useable envelope from a guitar signal.
Get *both* the envelope-filter/autowah article from geofex and the one at http://hammer.ampage.org
Although it probably needs to be updated, the one at my site has more content (RG posted an earlier version). The embedded graphics seemed to encounter some problems during the PDF conversion so the version at Geofex might be useful for being able to see everything.
Though he is quite modest about it, our own Steve "Uncle Boko" Giles has published a number of envelope-controlled filter projects in magazines with world-wide distribution. Indeed, after I regrettably sold my first MXR EF, I tried to regain some lost ground when I bought a pre-etched board and built the filter design Steve published in Electronics Today back in 1981 or so. T'wasn't until 2 decades later that I was flipping through my binders of schematics and realized "Hey, I know that guy!!".
I won't rewrite the paper here, but I will simply say that knowing lots about filters, and lots about signal rectification and envelope-followers, is helpful but it still won't tell you everything you need to know about envelope-controlled filters for guitarists. There is a lot more to factor in which respect to the kinds of things one needs control over, what you can or don't hear, and what design aspects make what sorts of impact on "feel" and usability.
Get *both* the envelope-filter/autowah article from geofex and the one at http://hammer.ampage.org
Although it probably needs to be updated, the one at my site has more content (RG posted an earlier version). The embedded graphics seemed to encounter some problems during the PDF conversion so the version at Geofex might be useful for being able to see everything.
Though he is quite modest about it, our own Steve "Uncle Boko" Giles has published a number of envelope-controlled filter projects in magazines with world-wide distribution. Indeed, after I regrettably sold my first MXR EF, I tried to regain some lost ground when I bought a pre-etched board and built the filter design Steve published in Electronics Today back in 1981 or so. T'wasn't until 2 decades later that I was flipping through my binders of schematics and realized "Hey, I know that guy!!".
I won't rewrite the paper here, but I will simply say that knowing lots about filters, and lots about signal rectification and envelope-followers, is helpful but it still won't tell you everything you need to know about envelope-controlled filters for guitarists. There is a lot more to factor in with respect to the kinds of things one needs control over, what you can or don't hear, and what design aspects make what sorts of impact on "feel" and usability.