[sdiy] DBX202 VCA questions

[JH.]

Lower noise.
That's an old trick: signal adds in a linear way, noise only adds geometrically.

JH.


----- Original Message ----- 
From: "cheater cheater" <cheater00 at gmail.com>
To: "synth-diy" <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, September 13, 2009 5:08 PM
Subject: [sdiy] DBX202 VCA questions


Hi guys,
I have been reading up on VCAs a little bit and found some more info
about the Harrison 4032 burried in Google results. It turns out that
they use the DBX202 VCA for the channel level. Researching a bit about
this, the gyraf.dk page says this about the 202:

http://www.gyraf.dk/gy_pd/ssl/ssl.htm

"The DBX 202XT VCA can be very hard to get these days, so I designed a
substitution circuit based on the THAT2180/2181 type VCA - a recent
version of the DBX2150 that SSL also uses for their channel
compressors. This substitute circuit is based on reverse-engeineering
a 202XT VCA - it turned out to consist of ten paralleled 2150's with a
common low-impedance buffer for the control inputs."

Now... why would they ever do that? DBX weren't just throwing in more
because they *could* were they?

One of my theories is that ten VCAs can deliver a higher output
current than one - and therefore, if the input impedance of what comes
after the VCA bank is not high enough to be 'ideal' (and that's always
the case), then the better current performance would give the VCA bank
more 'strength' to move what they're being fed into. This is a purely
uneducated guess.

What do you guys think?

Cheers
D.
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