TomG's VCF9a

[Romeo_Fahl at stream.com]

For those who are interested, the schematic for the circuit that Tom's filter is
 based on is at this URL:

http://www.spiritone.com/~8brain/schems/srgvcf.gif







"tomg" <vco at mindspring.com> on 05/12/99 11:08:22 AM
                                                              
                                                              
                                                              
 To:      "Haible Juergen" <Juergen.Haible at nbgm.siemens.de>,  
          "DIY" <synth-diy at mailhost.bpa.nl>, "Dr. Jörg        
          Schmitz" <schmitz at patho.bonn.com>                   
                                                              
 cc:                                                          
                                                              
                                                              
                                                              
 Subject: Re: TomG's VCF9a                                    
                                                              






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> IMO, it cannot work the way it was designed.
> Look at the loop gain around the inverting adder, noninverting integrator
> and inverting 2nd integrator.
>
> (Switch pins 13 and 14 of the 13600 and you have the familiar Oberheim
> scheme.)
>
> Strange that it's in the layout, too, so it can hardly be a typo.
> Does anybody test these layouts before they get published ??
> (Sorry Tom, no flames intended. But do you actually *build* all this stuff
> yourself ?)
>
> JH.

I think your opinion is wrong. I don't have time to go over it right this
minute, but I will. And yes I test everything before posting. I do not
always test pcb layouts. However I always state that it was untested
if that is the case.

I will get this out and help Jorg as soon as I can. Maybe a day or two.
I'm trying to get the vco4 shipped today. Please be patient Jorg. It does
work and does sound very good....I'll be back.

-tg