Is the filter build the same way in RF circuit and in audio circuit ?
And does it get a better noise reduction with a passive filter or with an op-amp active filter ?
The filter configuration described in the site you mentioned is used in narrow-band applications ..
If you need 80Hz to 1200Hz bandpass filter you should look at cascading a 1200Hz low-pass filter (LPF) and 80Hz high-pass filter (HPF) - or the opposite way around HPF and LPF.. see picture below ..
To make it workung correctly you will need an input buffer (voltage follower) and all this can be done with one IC (LM324, for example) which has 4 opamps in single package ..
Here is info on LPFs: http://www.ecircuitcenter.com/Circuits/opsalkey1/opsalkey1.htm
and here on HPLs: http://www.asahi-net.or.jp/~ZC4M-HGC/utils/hpf2nd.html
that's what I wanna do, a filter that oscillate. but with op-amp. high pass and low pass cut frequency but i juste want to attenuate or accentuate.
Am I in the good way
here is what I put on my breadboard
fisrt a pre-amp then the follower, and in parallel with the high pass, the low pass filter. and finally a comparator because I don't wanna cut all of the low or high signal
well my testings told me that the circuit up there is not quite correct. But the next generation works !! I made a lowpass filter, Chebychev style, with a cut off frequency of 1 kHz with a o.5 gain ...
thank IanP for your help
P.S. If anyone want help to make a wah pedal, contact me at cedric_somers@sympatico.ca i'll show you my project or give you aid.
It is a very intresting project ... see and work with different kind of filter
this circuit is not quite correct I work on it and i've found what's wrong ... it work but it's not fun to play with the effect. I'll show you my new generation