[Fwd: Re: [sdiy] dual prec. op amp options? (private)]

[Seb Francis]

I think this was meant for the list, not me directly.

And yes Michael I very much agree with you!  I can see no need to use an 
exotic/expensive high slew rate precision opamp for a VCA control voltage.


-------- Original Message --------
Subject: 	Re: [sdiy] dual prec. op amp options? (private)
Date: 	Thu, 21 Dec 2006 09:51:44 -0800
From: 	Michael Bacich <weareas1 at earthlink.net>
To: 	Seb Francis <seb at burnit.co.uk>
References: 	<5B06602D-E536-4AEE-9696-7F49F4563218 at ran.es> 
<458AA59C.7090208 at burnit.co.uk> <200612211745.40831.sdiy at haraldswerk.de> 
<458AC59B.9080206 at burnit.co.uk>



On Dec 21, 2006, at 9:34 AM, Seb Francis wrote:

> Even so, my point is that if a VCA takes 20us to switch fully on or  
> off (i.e. using a 0.5V/us opamp for a 10V control voltage) then for  
> a 10kHz input signal the entire slew time takes only 1/5  
> wavelength.  In practice it's unlikely even that the input signal  
> will have a frequency this high.

I think all of this discussion started with a question about what  
opamp to use for control circuitry around an SSM VCA.  DC control  
circuitry, not audio.  For that purpose, even a 741 could be referred  
to as overkill.  I'm joking, yes, but I think you take my point.

Mike B.