[b]EQ's [/b]- what are first and second order filters?

[Leftrights]

Can anyone give me a quick rundown on the difference between first and second order filters?  I always read the terms but I'm not quite sure what they mean. :?

Also can anyone point me to some schematics that might demonstrate the two types?

Thanks...

[keko]

Check Peter's post

http://www.diystompboxes.com/sboxforum/viewtopic.php?p=96528&highlight=#96528

[Mark Hammer]

Each RC combination in a highpass, allpass, or lowpass filter yields essentially a 6db/octave slope.  Cascading filter stages/section/poles gives a steeper slope since the filter sections are additive in effect.  A second-order filter is the same thing as a 2-pole filter.  I gather it is called a second-order filter because the filter poles are in series, so that you are filtering what has already been filtered.  Most things are labelled as "second-order" when another version of a process is applied over top a preceding one.

A nice example can usually be found in any of the chorus, echo or flanger effects.  For instance, looking at the schematic for the BOSS CE-2 chorus shows a 3-pole filter built around a single transistor just before the BBD/delay chip, each pole consisting of a resistor and capacitor.  This provides an 18db/octave rolloff response.  Given that there is a second such stage after the BBD, in all there are 6 poles' worth of lowpass filtering, or 36db/octave.

Most of the envelope-controlled bandpass filters like the Dr Q and Baseballs provide a filter response that is essentially 1-pole on each side of the centre frequency.  Traditional "Minimoog-type" filters on synths provided a 4-pole lowpass filter response.

[Leftrights]

Thanks alot.  That answers two questions that I had.  I always knew that 2 pole filters were two filters piled ontop of each other but I didn't know that that made the response steeper.
I've really become interested in EQ's over the last few weeks, there is alot to learn and all of it is great info....

Thanks

[Leftrights]

My message was posted twice and I went back to check it like a good little boy but I can't figure out how to get rid of it so I just changed it to this little explination so that you wouldn't have to read the same thing twice...

[Peter Snowberg]

Sorry, the delete thing was my error.  :oops:

Other forums have it and I see the option in my menu, but apparently it's not in everybody elses menus. Oh well. Thanks for making the effort.

Take