vocoders

[Kirke Sonnichsen]

The Synton used 54dB/va filters. Unfortunatley I've only heard
it. I've never been able to find schematics for the 221 (I share
your curiousity) but, Felix Visser, it's designer, did a 14 band
DIY beauty (w/24db/va filters )for Elektor in the 1980's (with a
followup article on a really nice voiced/unvoiced detector). I've
never heard the 14 band but, I've hear it sounds great. I'm sure
I've seen that stuff online somewhere but, I can't remember where...

- Kirke
(all these bands and no drummer)



>Lets say that you want to build a 18, 20, 22, band vocoder with steep
>filters (EMS style I guess).
>
>How do you go about designing a filter with such high Q (54db/oct)?
>
>Doesn't it become unstable?
>
>I have very little knowledge about filter design but I am still very
>curious.
>
>Are there any schematics for a 54db/oct bandpass?
>
>I assume there would not be pots if used in vocoder. So would this be simply
>a fixed frequency???
>
>------Original Message------
>From: Kirke Sonnichsen <kirke at lmi.net>
>To: grichter at asapnet.net, synth-diy at node12b53.a2000.nl
>Sent: October 31, 2000 11:47:06 AM GMT
>Subject: Re: vocoders
>
>
>Indistinguishable? I must strongly disagree! More bands does
>not necessarily make a better vocoder. As you divide the
>spectrum into narrower slices, the design of the filters becomes
>increasingly more complex. Not to mention that most vocoder
>algorithms in low cost multi-effects boxes have a linear
>distribution of band "centers" (which is less than optimal for
>speech synthesis) and don't have voiced/unvoiced sections!
>
>The 14 band vocoder "object" in the Nord modular series is a nice
>exception. No voiced/unvoiced detector but, as it uses a little
>less than 50% of the processor bandwith you can build one
>relatively easily out of the filter and logic objects provided.
>I've heard a rumour that it was designed by Felix Visser. Has
>anyone else heard this?
>
>While I'd bet in the near future we'll see some nicer digital
>vocoders, I have yet to hear one that begins to rival the
>inteligibility of the Synton 221.
>
>- Kirke
>(vocoding for dollars)
>
>>
>>You can pick up Boss SE-50 effects boxes for $50 nowadays and they have a
>>built in 22 band vocoder. An analog implementation would require several
>>hundred dollars in parts, and the results would be indistinguishable from
>>the $50 DSP unit.
>>
>>----------
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