Hi,

> I did not realise that something like this could be
> so complicated and it would possibly be easier to
> implement using analogue electronics but that
> would not be as much fun to play with


I'm not an expert in analog electronics, but how about
this: Design a notch filter RLC or RC-Opamp circuit
(RC-OpAmp is probably preferable -- no clunky
hard-to-find inductors), and then depending on how
many bands you want in your analyzer, use that many
notch filters and select component values so that the
upper cutoff frequency of a lower frequency filter is
equal to the lower cutoff frequency of a higher
frequency filter. Pass the input to all of the filters
in parallel, and you'll get seven (for a 7 band
analyzer) output signals that correspond to your
bands. Pass each of these through an envelope
detector, then measure the voltage of each signal.
That voltage can then drive a bar graph LED (for
example). There's a few circuits on the internet
already designed that convert a voltage signal to a
bar graph signal, just check some of the circuit
archives kicking around and you'll probably find
something.

That's off the top of my head... I hope none of the
analog pros on the list are shaking their head at me;
Maybe one of them can comment on the feasibility of
this approach. :)

T.



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