Vocoder Design questions

[Scott Bernardi]

First thing:
Is the "index" function working on synth-diy? I get back "No files
available for synth-diy". I wanted to see if my question had already been
discussed. I've looked through the archive, but it's pretty old (1996).

I'm looking at designing a vocoder just for my own self edification. I've
looked at the 1976 Elektor vocoder design, and read a bunch of threads
about the PAIA vocoder although I haven't seen the schematics.
My question concerns the bandpass filters. The Elektor version uses two
cascaded Sallen-Key filters for 24db/octave slopes. At two opamps plus 4
caps for each of the filters, that's a lot of components for the 16 bands I
want.
I've been considering using a single Sallen-Key bandpass (two pole) with a
higher Q (say about 6 for 1/3 octave spacing), and an attenuator to get rid
of the extra gain that is a byproduct (if you have access to them, the
Electronotes Application Notes AN-25 and AN-26 have a good discussion about
this).
Articles I've read say the real top of the line vocoders use 5th and 6th
order filters to get steep enough slopes to pack the passbands closer
together.
Is there a fault in my thinking about using higher Q two pole filters
rather than low Q higher order filters?
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Scott Bernardi
voice: 415-538-0439 (note new number)
fax:   415-904-8375
scott.bernardi at fritz.com