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A week ago (Vocoder thread), I said, based on my memory of examining the notion many years ago, that the idea of cascading two identical BP filters to sharpen Q was distressingly slow. </div>
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If I wrote this up in the distant past, I can't find it. Anyone?</div>
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I did it again:</div>
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<a href="http://electronotes.netfirms.com/ENWN58.pdf">http://electronotes.netfirms.com/ENWN58.pdf</a></div>
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and found cascading multiplies the original Q by 1.5537, for all Q. Did I make a mistake? </div>
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Nice-looking bandpass - just not much sharper Q-wise.</div>
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Bernie </div>
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