[sdiy] Wanted: non mathematical description of the function of RC-filters

[cheater00 .]

Florian,
the one thing that wasn't addressed in the explanations here, and is
confusing, is that you're not talking about the frequency of the
signal (as some have said), but the frequency of a partial. Filters
attenuate different partials differently. You first need to explain to
people what partials are, and show some frequency spectra. Then tell
them that each partial is considered separately and its gain at the
output depends on the frequency of the partial, not of the signal
itself. You could even take the voltage divider analogy and extend it.
So let's say you have something like a pipe coming in from the left,
of a specific thickness. It is split into three branches, called "high
frequencies", "mids", and "low frequencies". Those run horizontally in
parallel. Each of them goes into a two-way split. Depending on how
your voltage divider acts at the specific frequency, the relative
sizes of the branches of the split will be different. So if it's an
LPF, and you're at a low frequency, most signal will go to the branch
"to output", but just a tiny amount will go to e.g. the river or
something. Then at mids, equal amounts will go to the output, and get
dumped. At highs, there's a very thick pipe going to waste, and only a
tiny amount actually connected to the output.

Cheers,
D.

On Tue, Aug 6, 2013 at 10:35 AM, Florian Anwander
<fanwander at mnet-online.de> wrote:
> Hello
>
> I am answering this post, but I want to thank everyone for the very good
> suggestions (also Richie for his good ideas on private mail).
>
> First of all: the description shall be a short paragraph in an article for a
> german magazine a bit similar to soundonsound http://www.synmag.de/. The
> topic of the article will be the history of roland filters (the extended
> version of my page http://fa.utfs.org/diy/roland_filters/index.html). Maybe
> I will continue this later with other companies.
> So the description shall be only some short introduction how filters work in
> general. The reader shall at least be able to recognize the basic components
> of a filter in the schematics.
>
> The remark of Monty and others about starting with the voltage divider is
> great. I will combine this approach with my draft.
>
>
> Thanks for now to everyone. I will come back.
>
> Florian
>
>
> Am 06.08.2013 01:19, schrieb m brandenberg:
>
>> On Mon, 5 Aug 2013, Florian Anwander wrote:
>>
>>> Any better ideas?
>>
>>
>> If you can introduce the idea of a voltage divider of two resistors
>> in series, you could then take them along another step where one of
>> the resistors varies with frequency.  Now you have RC high- and
>> low-pass filters (ignoring phase, complex impedance and superposition).
>>
>> m
>>
>> --
>> Monty Brandenberg
>>
>
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