VCA designs

[Paul Schreiber]

1) If you want to control stuff with VC, a VCA is not the solution. Check out the Dallas Semiconductor and Xicor solid state pots. The Titans of Analog Synth will be using these extensively for VC, and they remember their settings when the power is off. AND you can hook 200 of them up over a 3 wire interface to any microprocessor made.

2) For a decent VCA, its hard to beat a Gilbert multiplier based on say a LM13600. See the PAiA Fatman schematic at www.paia.com.

If you really want a studio quality VCA, check out the fromer dbx stuff at THAT Corp. They sell the stuff used in $100K mixers. A single, basic VCA chip is around $35.

Paul Schreiber
Synthesis Technology

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From: 	Josh Rowe[SMTP:JROWE at everest.acpl.lib.in.us]
Sent: 	Wednesday, February 19, 1997 4:46 AM
To: 	synth-diy at horus.sara.nl
Subject: 	Re: In case I missed anything....

I usually just lurk in the background, but in this case I'm throwing
my 2 cents in, but I would also like to see any good VCA
designs ( high dynamic range/low noise ) that anyone has.

Some of the stuff I've gotten from the web, I'm skeptical of.  And I 
do have the Electronotes Builder's Guide/PCC, but those are dated and 
I'm wondering if a really good VCA can be had with and handful of op 
amps, etc.  Incidentally, I'd like to have a good VCA because I'm 
planning to build a modular that has VC of every parameter, and I'll 
need tons of VCAs for Env Depth, FM Depth, PWM Depth, etc.

--------------------------------------------------------------------------------------
Date:          Tue, 18 Feb 97 17:16:25 PST
From:          gstopp at fibermux.com
To:            synth-diy at horus.sara.nl
Subject:       In case I missed anything....

     Hi DIY, 
     
     If anybody tried to email me anything and got no answer (like ASM-1 
     queries), please re-send. I have been off-line for several days, till 
     this afternoon (Tuesday 2/18). Sorry for the bother! Any good threads, 
     I probably missed :(
     
     Corporate LAN problems.
     
     Anyway for lack of email I have had plenty of time to goof around on 
     the test bench. Some of the stuff I want to report about include:
     
     * A pretty cool voltage-controlled waveshaper
     
     * A real nice voltage-controlled full ADSR design
     
     * Modifying PC serial ports to work at MIDI rates
     
     Also - I want to find out if anybody has a high-performance discreet 
     VCA design. I'd like to know if there is a design that uses 
     easy-to-get parts, and would be something that a modular synthesizer 
     power-user would welcome into his system. You know, wide dynamic 
     range, ultra-low noise specs, things like that. Any help there?
     
     Hope I'm still subscribed,
     
     - Gene
     gstopp at fibermux.com

Josh Rowe
jrowe at everest.acpl.lib.in.us