VCOs, VCAs, and vocoders...

klund at MIT.EDU klund at MIT.EDU
Fri Jan 3 17:45:50 CET 1997


I'm currently working on/thinking about two little projects, and I was
wondering if you guys could offer a little advice...

I have built the Paia (clever design!) Shepard Function Generator,
http://www.hyperreal.com/machines/manufacturers/Paia/images/ and now I
want to produce the "barber pole" tones, so I need 8 VCOs and 8 VCAs.
What topology would give me a simple exponential VCO for a bank of them?
Should I just use a stripped-down version of Gene's ASM-1 VCO?  Also,
can anyone recommend a simple VCA topology?  I have a bunch of 3080's,
so I'd like to use them, if possible.

While on the subject of banks of VCA's, I've been thinking about
building a vocoder.  I was reading the archive, and I came across some
posts saying that an 8 channel vocoder isn't the best...  How many
channels should a good vocoder have?  How many octaves should it cover,
with how many bands per octave?  If anybody would be willing to send me
an example band, I'd really appreciate it.

Also, for the ASM-1, can the LM394 be substituted for the MAT-02?

Thanks,

--> Kent.



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