AW: TomG's VCF9a

[Haible Juergen]

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.

> ----------
> Von: 	Dr. Jörg Schmitz[SMTP:schmitz at patho.bonn.com]
> Gesendet: 	Mittwoch, 12. Mai 1999 09:01
> An: 	'synth-diy at mailhost.bpa.nl'
> Betreff: 	TomG's VCF9a
> 
> Hi all,
> 
> The last two days I tried to built the TomG's Serge SVF (Band/Low/High).
> (It's the VCF9a). Well, the problem is : it doesn't work. I first tried
> the PCB, then, after it did not work at all, I built it on a protoboard
> with the same result. I used the NE5517N. I tested it, it works. The 071
> too.
> And voltage supply and everything else was tested a lot of times.
> I don't think, that the differences between LM13600 and NE5517 are
> responsible
> for that (in this application). Am I wrong ?
> 
> any ideas ? 
>