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From: evalp@etek.chalmers.se (Laszlo Radanyi JR)
Newsgroups: sci.electronics,rec.audio
Subject: adjustable filters
Keywords: adjustable active filter
Message-ID: <1991May1.085534.29939@etek.chalmers.se>
Date: 1 May 91 08:55:34 GMT
Sender: evalp@etek.chalmers.se (Laszlo Radanyi JR)
Organization: Chalmers University of Technology, Gothenburg, Sweden
Lines: 24


I got a new problem when I moved to my new place. When I set up the hi-fi, 
the bass seemed to floooow away. I didn't even know my speakers could produce 
that low bass. 
Very soon, the idea of a filter came up. It's no big deal to make a filter
for a specific break frequency and with a certain slope, but how do you do 
this when you want to adjust both ? 

I would like to make a low-pass filter with break frequencies between
30 and 300 Hz, and slopes between 6 and 24 dB/octave. 

The nearest solution I have is a kind of paramethric tone control which 
enables +-10 dB ( custom adjustable ) between ca 40 and 400 Hz. Would be OK,
but I wonder if my idea is possible.

If it is not, there would be an easier solution: make a filter with variable
break frequency and level. The problem here is to switch between a number
of components on a PCB at the same time. I would prefer some sort of digital
setting - that makes it even worse. How on Earth do you adjust frequency AND
level with one or two components ??

Every suggestion is warmly welcomed. Thanks.

laszlo as. evalp@etek.chalmers.se