QRe: [sdiy] Reprinting Electronotes

[jbv]

Ian ,

> But if someone wants to make a filter bank, well, jeeze, that's a really
> simple thing to figure out how to do.  Most of the relevant non-obvious
> information has been posted (for free!!!) on this thread.
>
> Here's what you do:
>
> 1.  Pick out a good low noise opamp.
>
> 2.  Search the web or some textbook for opamp bandpass circuits.  There are
> zillions around.
>
> 3.  Pick a circuit and use the textbook equations to design a set of
> filters with Q of 25 and frequencies spaced at a ratio of 2.1^(1/5).
>
> 4.  Design a mixer (or just a summer) circuit to combine all the outputs.
>
> 5.  Add some feedback to vary the Q.  (Either locally, in sub-banks or
> globally. You get to choose!)
>
> 6.  Build it and tweak up all the frequencies.
>

Great, you're answering my questions before I find the time to ask them...

As for "frequencies spaced at a ratio of 2.1^(1/5)", how many bands per
octave does that mean ? Three ? Five ?
And what are the practical frequency limits (both high & low ends) for
such a module ? 100 Hz to 10 KHz ?

Thanks,
JB