How do you LP wo/caps?

[Magnus Danielson]

From: "tomg" <efm3 at mediaone.net>
Subject: How do you LP wo/caps?
Date: Thu, 27 Jul 2000 18:13:49 -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! Actually
> it doesn't have much of anything.
> 
> 1 - dual pnp
> 1 - dual ota
> 2 - pots
> 16 - resistors
> 
> The upper range is especially clear and transparent almost
> sparkling but it roars down into to lower range. Notably 
> when oscillating the sine is very symmetrical and uniform. Being 
> stable to less than 1Hz. It really sounds terrific...No 
> kidding!
> 
> It's done with multiple feedback paths. Without me giving 
> too much away, has anybody ever seen anything like this 
> before?

Yes, they are called misstakes. These are what form new ideas for solutions.
May I be the first to congratulate you for your discovery!

This is just how the Aphex sweetener (or whatever it is called, broken memory
cell needs replacement?) came about, they where according to history about to
assemble a cheap amp-kit when something was broken and became usefull...
instead of "fixing" it they reverseengineered it and patented it.

Now, how does the topology look, I AM eager to learn this ;)

I see LOADS of caps in there ;)

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.

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? ;)

So, hand over the topology for the eager one! ;)

Cheers,
Magnus