QRe: [sdiy] Reprinting Electronotes

[fmg]

Ian Fritz wrote:
> 
.................
> 
> 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.
> 
> That's it.
> 
> If someone just rips off the old EN circuits then they don't learn anything
> and they give up the possibility of customizing the unit for their own
> needs.  It's really sad that anyone would want to go that route for such a
> simple device.
> 
>    Ian


Excellent suggestion. This is the best explanation on how to
build a filter bank that I ever heard (seen/read).

That's the kind of recipe I prefer instead a pile of schemos (and what
makes to some of my friends wonder why I love and collect Application
Notes that (apparently) point to nowhere..)

(While most ANs simply point to no other direction than the device involved,
most of them "open" some doors; the direction to follow then fall in the
domains of one's creativity)

If I decide someday to build a FB I'm sure that with those 6-points I
have almost everything and have saved a lot of time (or pain) in the
process.

Thanx for the pulse

Fabio Gonzalez.
Posadas, Argentina