All these filters and no maths...

[frank_p]

Frank, what kind of filters do you have in mind?

Anything valuable filters for audio.  I began to make small perfboards with everything soldered to nails on top of it.  Then I put them on Masonite and finally, Velcro (all glued in a sandwich).  I don't box anything.  Just lay the little islands on a mat and wire them together with alligator clips, springs, speaker connectors or screw terminals. 

A bit like the fxbus, or in a analog synth, except that everything is accessible and as simple as possible.
Forget about noise, and PCB.  Just for study and probing.

Some ago I solved the big muff tone stack, input sine wave and a low output constant load. I solved the set of diff eqs using a classical mechanic technique: if you solved vibrating systems you know what I'm talking about, no need to go Laplace. After all, either way, the difficulty is the same. 
The beauty of solving a filter the old fashion (or vintage) way is that you see exactly what's going on.

True but I am a bit more used to Laplace (and most often lazy).

This thread got me thinking about analog computers. They don't teach this anymore but in my opinion it is an invaluable tool for these kinds of situations. It operates on the principles that resistance, capacitance and inductance are analogous to concepts in other completely unrelated fields. Like in mechanics with springs, dashpots, and masses, they can be modeled using a circuit. And it spits out answers to Diff EQs immediately. But its quickly becoming a lost art.

Joe, you are talking about something that I have heard of but really don't know about.  This looks a lot like some of the models for viscoelastic materials: where you have different springs, dampeners and masses connected in series and in parallel so as to modelise as closely as possible some rheological materials.

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Also, thanks George for the updates about the softwares. 

[mac]

I have to read all those links. I need to refresh my mind.
I remember how to solve diff eqs but I forgot a lot of physics concepts.
Besides, I did not study circuits the way EE do.

mac

[frank_p]

I have to read all those links. I need to refresh my mind.
I remember how to solve diff eqs but I forgot a lot of physics concepts.

For me, it works in the other way. I really have to push myself to get good at maths.  Once that is done, the rest is butter.

Besides, I did not study circuits the way EE do.

Me neither.    Otherwise I would not be asking all these questions.  All that I have in my head is structures, unbalenced motors, rubber dampner, ropes, belts, carbide cisels, etc.  I have great respects for EE and physicians, their work is far more abstract.  On the other side, I am really tired of process E and industrial E.  It's just that it's not in my personality I guess.

Today is germanium param. measuring day.  Those are real temperature measurment devices...
I am going to put gloves to manipulate them.