How the $@#! do you FM mod a ladder filter?

[Magnus Danielson]

>>>>> "c" == cyborg0  <cyborg0 at GlobalEyes.net> writes:

Hi!

 c> Okay, I need to know some of the basics and caveats of FMing a ladder
 c> filter. Where do I inject the signal? It would make sense to inject it
 c> into the cutoff CV, but, could it cause damage? i know i should prlly
 c> put an attenuation pot in there and a coupling cap, but it seems there
 c> would be more to it..any answers?

Just apply the signal to cutoff CV, as usual. A DC block cap or not is
up to you, but a pot could be usefull.

Unless you apply normal voltages you should not be able to destroy
anything in the filter, this given that it is not insanely incorrect
in its design and dimensioning. Just give it a little touch of the old
ESD black magic and you will be out safe.

 c> 	also, how does one identify where the poles are? can the response of
 c> these be manipulated as in the Jomox Sunsyn? 

If you are talking about poles as in poles and zeros then you have to
make the rough model of the cursuit transformed into a cap and
resistor thing where the transistors having caps on their emiters
transforms into variable resistors. You must recall that the feedback
of the differential value on the top capacitor when being applied to
the common emitter transistor-pair in the bottom of the ladder will
provide the feedback that moves the poles around.

There are some signs that one should be able to change property quite
a lot but I haven't done the homework properly to tell you how well it
will work.

Cheers,
Magnus