[sdiy] vocoder : synthesizer part

[jhaible]

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
>