SV: Re: Re: SV: Re: SV: [sdiy] QVCO schemo up

[karl dalen]

--- Ian Fritz <ijfritz at earthlink.net> skrev:

> At 08:04 AM 11/12/05, JH. wrote:
> > > infact this cirquit is nothing more then a variation of the SVF!
> >
> >Sure - what else should it be?
> >It's a 2nd order differential equation in the most direct realisation.
> >If it's dampded, it's a filter. If it's not, it's an oscillator. The art
> >lies
> >in keeping it _just_ so undamped, that it oscillates without increasing
> >amplitude.
> 
> Right.  In fact the AD handbook writeup presents it as a state-variable 
> oscillator and indicates on a drawing how to use it as a filter.
> 
> This brings up the possibility of making a synth module functioning either 
> as a SV filter or quad osc.  In fact, one could probably make a small 
> add-on circuit with a panel switch to hack up existing SV filters to add 
> the quad osc function.

Then you can aswell take one OSCar filter stage exchange the
darlington buffers for fet amps and slightely adjust the feedback 
loops gain structure and have a very nice filter/oscillator, 
particularely the filter mode would be much more stable then 
this cirquit!

KD