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DIY Stompboxes => Building your own stompbox => Topic started by: xcpointx on August 16, 2004, 10:56:46 AM

Title: What is the name for this filter circuit design?
Post by: xcpointx on August 16, 2004, 10:56:46 AM
I was just wondering if there is a 'technical' or 'proper' name for the design of these 2 filter circuits...

(http://www.crossingpoint.za.net/quadx/pre%20midi%20schematics/filters.gif)

I want to change the component values of the upper one, to match that of the lower one... (so that both are the same!)
Title: What is the name for this filter circuit design?
Post by: xcpointx on August 16, 2004, 11:11:22 AM
ok i may have answered my own question... but from info ive found on the net it looks like a form of
'cascaded Unity gain High/Low Pass Filter' or Sallen Key??

but it isnt cascaded. so what would the correct term be?
Title: What is the name for this filter circuit design?
Post by: Rich G. on August 16, 2004, 11:45:49 AM
Bandpass Filter. ?
Title: What is the name for this filter circuit design?
Post by: Tim Escobedo on August 16, 2004, 11:47:06 AM
I'm guessing "cascaded Sallen Key" may be correct. Since it's basically two second order bootstrapped filters in series.
Title: I'm with Tim
Post by: MR COFFEE on August 16, 2004, 12:23:40 PM
The values and frequencies are far enough apart they don't interact very much.

What's it out of? :?:
Title: What is the name for this filter circuit design?
Post by: Gilles C on August 16, 2004, 12:49:24 PM
To me, it' a multiple-feedback 2nd-order bandpass filter combined with a sallen-key 2nd-order active low pass filter.

That must be to go even lower than with the bandpass alone.

Funny thing, late last night, I was looking about what kind of configuration was used in a cab sim schematic I have, and read some info about your kind of filters.

The configuration I was searching for was, I suppose, a double sallen-key 2nd-order active low pass filter.

So the circuit looks like yours, but with another salen-key in place of the bandpass filter.

Gilles

Added: I looked in my history/favorites to find the pages I was talking about...

http://www.uwm.edu/People/msw/BodePlot/index.html

http://www.national.com/an/AN/AN-779.pdf

So after reading that again, the circuit I was looking for (a double sallen-key) was a sallen-key 4th-order active low pass filter   :shock: :roll:  :?:  :?:
Title: What is the name for this filter circuit design?
Post by: xcpointx on August 17, 2004, 03:14:36 AM
Awesome! Thanks for all your responses

Is there a formula to work out component values according to desired cut off frequencies?
Title: What is the name for this filter circuit design?
Post by: toneman on August 17, 2004, 09:09:44 AM
Gilles,
nice links!
good nfo!
thanx!
tone
Title: What is the name for this filter circuit design?
Post by: Gilles C on August 17, 2004, 10:08:38 AM
Quote from: xcpointxAwesome! Thanks for all your responses

Is there a formula to work out component values according to desired cut off frequencies?

Check this link

http://www.linkwitzlab.com/filters.htm

If you want a little more details, get a coffe and read these...

http://www.maxim-ic.com/appnotes.cfm/appnote_number/738

that came from

http://www.maxim-ic.com/appnotes10.cfm/ac_pk/4/ln/en

This is nice

http://www.beis.de/Elektronik/Filter/Filter.html

Added: There is a program to do the calculations:

http://www.download.com/FilterPro/3000-6677-10215352.html
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