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Looper's Delight
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>Charles Zwicky wrote: > >>The delays used in an allpass filter are typically very short, and >>measured in samples rather than mS... > >At least in Bidule the delay parameter for Allpass is measured in mS. >In freeverb the range is from 5 to 15mS. Certainly not within the range where you would hear them as a discreet delay... > >As I understand it, it's intended to be a way of having a delay >with feedback, but arranged so that there's no comb effect on >sustained notes. No, not at all.. it's effect is diffuse an impulse. Try putting one in the feedback loop of a delay line with a coefficient of about 0.5 and you'll hear what I mean... > > >>I'm not sure that you meant to write "phase dispersion"... > >Just meant that different frequencies are delayed by different amounts. >(Allpass is also used in a phase fx.) It's an entirely different implementation than what you'd typically find in an analog "phase shifter". > > >>Try to think about the topolgy in a different way. If the allpass >>network is located after the loop, > >sorry, I took your description below to mean that there >was a "loop of allpass filters". > >> >>>Charles said >>>>in fact most digital reverbs consist of a loop of allpass filters* This comment is referring to a non "constant density" reverb, for example as in a Lexicon and Ensoniq reverb. As I pointed out above there are several ways to do it. It's likely that the EH "Freeze" uses a series of allpass filters before and after a fixed delay line. > >;-) >andy Yep... |-O -- ... http://www.zmix.net http://www.esession.com/ChuckZwicky http://albumcredits.com/zmix