Thank you for that, Aaron....I almost forgot that is what the z-filter it referred to and all those years of engineering of sampled data theory... Glad to see you back again....Happy New Year ! Were you able to help Jane with her question on detecting available output ports.....she just finished an editor for the P2K that is extends it's usefulness into the rest of the XL-X family.... Bob El Segundo, CA ----- Original Message ----- From: Aaron Eppolito To: xl7@yahoogroups.com Sent: Sunday, January 11, 2009 4:50 PM Subject: Re: [xl7] Re: z-plane - is it "all that"? Z-plane doesn't actually have anything to do with "morphing" or interpolation. They are filters designed around the mathematical construct of the z-plane, which is the discrete version of the continuous s-plane. Gross oversimplification is that instead of representing filter coefficients in the time domain, they're represented in the frequency domain (by using the z-transform, the discrete equivalent of the Laplace transform). Techie info here: http://en.wikipedia.org/wiki/Z-transform#Zeros_and_poles - Z-transform - Wikipedia http://en.wikipedia.org/wiki/S-plane - S plane - Wikipedia http://dspcan.homestead.com/files/Ztran/zlap.htm - Z Transform and Laplace Transform, applet Unfortunately, the z-plane filters appeared first in a product called "Morpheus", highlighting the morphing ability of these new filters. Since marketing something techie is usually pretty hard, E-mu pretty much said "Z-plane filters let you morph between X and Y!" I don't blame them since can you imagine reading one of the above wikipedia articles on a piece of advertising copy? That said, there *is* a grain of truth to the whole "Z = morphing" misconception. By modeling your entire filter as individual poles and zeros, you could modify each pole or zero individually, letting you dynamically alter a filter into a completely different kind of filter. The filter chip in the E-mu products has one hardware interpolator, allowing it to go from one set of filter coefficients to another in hardware. This also means that it only has one hardware degree of freedom (hence the only dynamic parameter being Fc). To do other realtime manipulations, the software has to load a whole other set of coefficients, then use the hardware to switch to them smoothly. This takes a lot of CPU, and can sound choppy if not updated frequently enough. It is, however, really really cool when it sounds right. -Aaron (updated with links) ----- Original Message ---- From: Alwyn <zardac@...> To: xl7@yahoogroups.com Sent: Sunday, January 11, 2009 3:08:03 PM Subject: Re: [xl7] Re: z-plane - is it "all that"? I remember reading about the morpheous and the emu, and as far as i am able to tell, the 'Morph' stuff is actually a combination of the frequency and the resonance controls, as there wasn't any other options that seemed to make sense.. i could of course be completely off the mark with that though. [zar] > I am wondering the very same thing myself. I'm looking at the manual, > and it's talking about a Morph parameter, which is how the filter > should change over time, but I can't find anything in the machine > itself. I get the feeling the manual section was copied from somewhere > else, and is rather misleading. Please, someone tell us that it is not > so!? > ------------------------------------ Yahoo! Groups Links [Non-text portions of this message have been removed]
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Re: [xl7] Re: z-plane - is it "all that"?
2009-01-12 by Bob S.