WG: VCA (was:: Re: In case I missed anything....)

[Haible Juergen]

 ----------
Von: Haible_Juergen#Tel2743
An: Magnus Danielson
Betreff: VCA (was:: Re: In case I missed anything....)
Datum: Mittwoch, 19. Februar 1997 12:18

>  g>      VCA design. I'd like to know if there is a design that uses
>  g>      easy-to-get parts, and would be something that a modular
> synthesizer
>  g>      power-user would welcome into his system. You know, wide dynamic
>  g>      range, ultra-low noise specs, things like that. Any help there?
>
> Didn't Juergen have a VCA matching that description built out of BC550s
> and BC560s?

I am not sure if "my" VCA would be the right one here. "My" VCA is
basically a Minimoog (dual) VCA from topology, only that the first VCA
stage is x4 in parallel for filter mode scanning, and the second stage
is x2 in parallel for pan modulation. I am sure it is a great VCA for
a *synth* (well, it's in the Minimoog ...), but it is surely not a VCA
for
general applications (no linearisation in there, just some raw
differential pairs). In one single synth voice distortion is a different
thing than for complex signals.

For general attenuation stuff (foot pedal etc ...) I use photo resistors
(LDR)
all the time. For my CX-3 organ, for example, I have build a rackmount
FX device with spring reverb, chorus and resonant filter - and with an
optoelectronic VCA. Just a LDR and a LED glued together. I used to run
this with a Volume pedal.
But recently I have found these wonderful optoelectronic stereo volume
pedals
from Yamaha, and use them instead. They are cheap (DM120,-) and very
heavy and sturdy. A completely different category if you compare them
with the plastic Roland or Korg types which I also have.

JH.