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Musical-Applications-of-Microprocessors-2ed-Chamberlin-H-1987

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496 MUSICAL ApPLICATIONS OF MICROPROCESSORS<br />

E!o-----,--1,o~O'""'0--...,2,...,,0!-:'0c:"0--c:"3,-fcio:-:0:-----:4'"",O':-OO=----<br />

FREOUENCY (Hz)<br />

(A)<br />

270<br />

CJ<br />

7~<br />

~ ...J<br />

ị .,<br />

1Il<br />

«<br />

:I:<br />

0..<br />

180<br />

90<br />

'"«<br />

...J<br />

-180<br />

-270 FREQUENCY (Hz)<br />

(B)<br />

n~_~<br />

o 100 200 300 400 500 600 700 BOO 900<br />

FREQUENCY (Hz)<br />

O~-':;:I:::::i:!:::::::J.==""""'....<br />

(C)<br />

1k<br />

IB0-<br />

j<br />

0<br />

~<br />

90<br />

~ -90<br />

«<br />

:I:<br />

0.. -/80<br />

FREQUENCY<br />

(0)<br />

(Hzl<br />

Fig. 14-10. Phase and delay graphs. (A) Delay versus frequency <strong>of</strong> 500-fl-sec<br />

delay line. (8) Phase versus frequency <strong>of</strong> 500-fl-sec delay line. (C)<br />

Delay <strong>of</strong> a highly dispersive filter. (D) Phase <strong>of</strong> a highly dispersive<br />

filter.<br />

(proportional to area under a curve) <strong>of</strong> the delay curve. As a result, only one<br />

curve is needed to fully characterize the delay/phase behavior <strong>of</strong> the filter.<br />

For musical purposes, the most useful all-pass filters exhibit nonlinear<br />

phase shifts and therefore time delays that vary with frequency. This means<br />

that a sharp transient, which contains a wide range <strong>of</strong> frequency components,<br />

will exit from the filter with the frequency components separated and

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