[sdiy] SVF resonance overdrive problem

[Andrew Simper]

Whilst on the SVF topic, I've got an Analog Systems RS110 and it sounds
fantastic. Does anyone have any idea what structure and components they are
using? http://www.analoguesystems.co.uk/anasysinteg/modules/rs110.htm

I think it's an SVF, but it's one that drives really nicely. The external
resonance path is also cool, and I've worked out this can be done with a
regular SVF structure - you just need to switch the internal resonance op
amp to x2.0 when you plug in an external signal (ie no resonance), and
invert the external signal coming into the res input path - that way if you
plug in the res output (which should be the bandpass output - hmm I should
check that) and gain it by x2 with a vca then you cancel out the internal
signal and get your regular self oscillating resonance.

Andrew 

-----Original Message-----
From: Harry Bissell Jr [mailto:harrybissell at prodigy.net] 
Sent: 12 December 2006 21:14
To: Dave Manley
Cc: Andrew Simper; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] SVF resonance overdrive problem

They do nothing. They are wired in such
a way so that they do not float (might pick up noise etc).

H^) harry



--- Dave Manley <dlmanley at sonic.net> wrote:

> Harry Bissell Jr wrote:
> > This circuit is really two independant VCFs...
> > one is a state variable (Odyssey) and the other is a (oops... Moog) 
> > ladder LPF (ARP2600)
> I have seen this schematic for the "40235" before but never really 
> looked at it.
> The ladder circuit is different from the 4012 used in the 2600.  
> Reading the notes I see it is actually the ladder filter from the 
> Odyssey.
> 
> What purpose do the diode wired transistors u4a and u5a serve?
> 
> What does u6a do?
> 
> -Dave
> 





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