[sdiy] vocoder : synthesizer part

[James Patchell]

http://www.grizzly.com/catalog/2004/483.cfm?

At 06:32 PM 3/27/2004 +0100, jhaible wrote:
>Some Vocoders use a pwm'd switch as a VCA - you can only do this before
>the filters.
>Also, BPFs after the VCAs will ring / decay smoothly even if the VCA
>would shut down very fast.
>
>JH.
>
>-----Ursprüngliche Nachricht-----
>Von: Magnus Danielson <cfmd at bredband.net>
>An: <jbv.silences at club-internet.fr>
>Cc: <synth-diy at dropmix.xs4all.nl>
>Gesendet: Samstag, 27. März 2004 15:43
>Betreff: Re: [sdiy] vocoder : synthesizer part
>
>
> > From: jbv <jbv.silences at club-internet.fr>
> > Subject: [sdiy] vocoder : synthesizer part
> > Date: Sat, 27 Mar 2004 13:08:46 +0100
> > Message-ID: <40656ECB.63102EBD at Club-Internet.fr>
> >
> > > Hi,
> > >
> > > I just noticed that in the synthesizer part of a vocoder
> > > the design can vary : some (like Elektor vocoder AFAIR)
> > > place the VCA after the BPF, while others (like Roland
> > > SVC-350 or the Moog vocoder) place the VCA before the
> > > BPF.
> > > Is there any good reason to choose one design or the other ?
> >
> > Depends on your VCA and your filter. If you have a noisy VCA, you place
>the
> > filter after it to filter out the noise, but if you have a noisy filter,
>the
> > VCA will only open it up when there is signal anyway.
> >
> > Then there is those where the "VCA" has alot of extra energy, so the
>filter
> > goes afterwards anyway.
> >
> > From a theoretical point of view (noiseless and distorsionless ideal)
>putting
> > them one way or another is equalent, but it is the flaws and how you best
>hide
> > them which really decides which way to go. Recall that you have this flaw
>times
> > the number of channels your vocoder has, so they add up quite quickly.
> >
> > Cheers,
> > Magnus
> >

         -Jim
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