🚀 go-pugleaf

In article <1992Dec18.133346.7262@sol.ctr.columbia.edu> brown@ccit08.duq.edu (Jason Brown) writes:
>Anyway, it occurs to me that using some combination of resistors and  
>capacitors in an RC circuit one should be able to filter out all but a  
>given frequency from an analog audio source.  The ultimate goal here would  
>be to set up a number of filters at different freqs. and send the output  
>of these filters to log. dot/bar display drivers yielding a spectrum  
>analyzer.

It's hard to make RC circuits that do well at this.  They tend to have
wide passbands with gradually-sloping edges, and to lose a lot of the
desired signal in the course of attenuating the rest.

Fortunately, there are prepackaged filter ICs that do an excellent job
of this kind of thing.  The buzzword to look for is "switched-capacitor
filter".  National's MF01 was the pioneer, but I'm sure there are better
ones now.
-- 
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  henry@zoo.toronto.edu  utzoo!henry