[sdiy] MOTM 440 4P LPF questions

[Dave Manley]

On 10/30/2011 2:30 PM, David G Dixon wrote:
> I saw and heard a MOTM 440 in action at the PNW synth meet (thanks, John
> Rice, for letting me ruin your patch!), and I have a couple of questions
> about it.  (It sounded wonderful, by the way, so if my questions are taken
> as criticism, that is certainly not my intent.)
>
> If these questions are impertinent, or if answering them would involve
> giving away state secrets, then feel free to slap me down.  Otherwise, here
> goes:
>
> 1) Can anyone tell me which stage's output is being fed back for the
> "Enhance" setting?
>
> 2) This additional feedback is obviously at fixed gain.  What is it?
>
> Here's a more philosophical question:
>
> 3) Why should a "discrete OTA" give any better results than an IC-based OTA
> or VCA?  After all, an IC is discrete on the inside.  (A direct comparison
> of four different 4P filters, some discrete and some IC-based, on
> Muffwiggler today would seem to debunk this whole "discrete" business, given
> that they all sound identical, which suggests that this whole "discrete"
> argument might just belong in the same category as the various gold-plated
> audiophile claims we often laugh about here.  I'm just curious as to the
> reasons why such circuits would or should be better.)

You could try asking Juergen Haible, IIRC he is the 440 designer.

-dave