[sdiy] CA3280 VCA Design

[Jay Schwichtenberg]

One question I have is about using the linearization diodes. Obviously
you'll get some SNR improvement by using the diodes. But, I've gotten the
impression (I can't remember if it was from the data sheet or the
Electronotes discussion) that if you drive the diodes input with a current
source vs. a resistor that you can get a few extra db on the SNR. I think
that might be what Paul does with the MOTM VCAs.

Any comments?

Thanks.
Jay S.


-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of James Patchell
Sent: Sunday, November 20, 2005 10:26 AM
To: Rob Keeble; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] CA3280 VCA Design


You might try looking here:
http://www.oldcrows.net/~patchell/archives/archives.html

and here:

http://www.oldcrows.net/~patchell/smb1/smb.html

lots of other crap on my website as well....

At 05:20 PM 11/20/2005 +0000, Rob Keeble wrote:
>Hi,
>I have a tube of CA3280's which I plan to turn into dual VCA's, however I
>can't find a circuit design on the web...so I have cobbled one together -
>which is here (37k GIF) - mainly using ideas from the SCI Prophet 5..
>
>www.emulatorarchive.com/assets/vca.gif
>
>Before I put this on the breadboard, any changes I should make?
>Audio and CV ins are 0 to +10V standard. VCA is linear, unity gain, and
>should't invert signals. Only one VCA shown...
>
>Many thanks
>Rob
>www.emulatorarchive.com

         -Jim
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