of Microprocessors

60 MUSICAL ApPLICATrONS OF MICROPROCESSORS
decay is related to the filter's bandwidth or Q with narrower bandwidths
(higher Q) resulting in a slower decay.
As mentioned previously, more complex filter amplitude response
shapes may be obtained by combining basic shapes. The most predictable
method for combining two shapes is to cascade two filter sections by feeding
the filtered output from one filter into the input of another. The resulting
response shape is just the point-by-point sum of the individual response
shapes, provided that they were plotted in decibels. Values from a linear gain
scale would have to be multiplied together for the result.
This technique is frequently used to get sharper cutoff filter shapes than
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w -25
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-55
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3
HARMONIC SPECTRUM
(0)
Fig. 2-6. Effect of filters on a square wave (cont.). (0) High-pass filter.