How do you LP wo/caps?

[Magnus Danielson]

From: "tomg" <efm3 at mediaone.net>
Subject: Re: How do you LP wo/caps?
Date: Thu, 27 Jul 2000 21:51:58 -0700

> 
> > > I am not sure what I have done! But on my bench right now
> > > is a 2 stage (pole?) LP filter that sounds much better than
> > > most of the 2 or 4P LP group that has no caps!
> 
> > Yes, they are called misstakes. These are what form new ideas for
> solutions.
> > May I be the first to congratulate you for your discovery!
> 
> Yep! LOL.;-)  you are right on about that one! It was a total mistake. I
> never
> intended for it to work this way.
> 
> > This is just how the Aphex sweetener (or whatever it is called, broken
> memory
> > cell needs replacement?) came about
> 
> I remember that story..

Yeah, remember Newton... he never sougth the gravity, but then an apple had the
good taste of accidently drop on the distinguished gentlemans head, and this
(according to the story as being told) made Newton come up with the idea of
gravity. I bet he ate the apple while pondering and meditating over the
willingness to fall that the apple seemed to have.

> > There are examples of filters where you take the builtin compensation cap
> of
> > an OTA and use that. Actually, this is what you can consider the Moog
> ladder
> > to be.
> 
> I thought about that but there are none in the 13600.

No needed, you have stray capacitance all over the place! These NP junctions
have a voltage sensitive capacitance. Then there is stray capacitance all over
the place... SiO has a rather large constant, something which the front chip
companies (IBM, Intel etc) is figthing to reduce by replaceing SiO with other
materials. Interestingly enougth is air one of them... ;)
Well, anyway...

Go and fetch the LM13700 Spice model and toy around with it. It is not
extremely accurate since it models only the dominant pole (no, no dominant
male), but it is enougth to get the hang of what is happening in there...

> > Capacitance is present in all curcuits, heck, it's there even when we try
> to
> > have nothing and not doing electric curcuits.... even vacuum has it ;)
> > Oh, yes... there is a find method for doing filters without caps, they are
> > called inductors, have you met those? ;)
> 
> Yeah, but how come it sounds like this!
> 
> http://www.xavax.com/efm/waves/no-caps.mp3

Hmmm... I gotta fix that bloddy sound-problem I have... I bring it over to
my laptop, reboot it into Win95 and listen... eh... don't ask why!!!

> > So, hand over the topology for the eager one! ;)
> > Cheers,
> > Magnus
> 
> I would love to Magnus!! I can't think of anything I would enjoy more..
> There is that problem of it becoming a hot new product for somebody.
> OTOH Maybe....We'll see..;-)

Well, strip out everything not needed and then let us have it ;)

Cheers,
Magnus