new here plus a question...

[Martin Czech]

:::Well, if nothing else, it would teach me how to 'convert' a schematic
:::analog linear system to a digital one. What I really need is a
:::tutorial/book/... that tells me how to build a digital approximation of an
:::analog schematic.
:::
:::No fancy stuff like modeling the non-linearities!


Ok, now I understand, a more or less academic training...  A good
introduction on this DSP stuff is still Rabiner/Gold.  It gives you a
solid background on discrete signal processing and all the little devils
and odds that are hidden within.  Without a good background like that
you'll never succeed, I guess.  Since the book covers a lot of topics
it can't go very deep into the details of filter design. But you can
follow the literatur list in this book.  I have no other book, and so
far it had all I needed.

So how do you start? You could simulate or measure the magnitude
phase response. Or you could guess/measure the poles and zeros of the
individual sections of the circuit. Of course only the dominant ones.
Anyway, the result will be a desired magnitude/phase plot inside Fs/2.

Now you can apply what you have learned about filter design methods
in order to get a more or less good approximation.  The real problems start
if you also want to model "knobs", these will move the poles and maybe
zeros in the original circuit. In order to emulate these knobs you need
to analyse root loci and transfer that from s-plane to z-plane.
Of course with some added zeros and warped root loci.

This is not covered in any text I know, because these assume fixed
root loci.

Via convolution you can get a fixed frequency response automatically...

m.c.