[sdiy] vocoder : synthesizer part

[Magnus Danielson]

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