Allpass filter design using passive components

Zodiac · 16th September 2003, 08:01 PM

Does any1 have any experience of using allpass filters in audio?

An allpass filter does not effect the amplitude of any signal, but it does effect the phase. Hence it can be used to correct the phase shift caused by use of Butterworth-type filters. Does any1 know how to do this?

Also, has any1 compared (listened) to the difference between a lowish order Butterworth and a highish order Bessel? I recall that Thorsten and Elso Kwak have a different approach to this in their treatment of filtering in non os dacs, but what is the difference in sound between a perfect square wave response, higher order Bessel and a phase shift (distorted) low order Butterworth.

Maybe I should just build them both and tell you!!

bknauss · 20th September 2003, 02:21 PM

Zodiac, I know you are looking for a passive filter, but I know of an active design using only op amps and resistors. Give me an email if interested. bknauss@eudoramail.com

advance · 20th September 2003, 05:13 PM

This link might help....

http://www.filter-solutions.com/passive.html#allpass

advance

16th September 2003, 08:01 PM	#1
Zodiac diyAudio Member Join Date: Jun 2003 Location: Kenfield, CA, USA	Allpass filter design using passive components Does any1 have any experience of using allpass filters in audio? An allpass filter does not effect the amplitude of any signal, but it does effect the phase. Hence it can be used to correct the phase shift caused by use of Butterworth-type filters. Does any1 know how to do this? Also, has any1 compared (listened) to the difference between a lowish order Butterworth and a highish order Bessel? I recall that Thorsten and Elso Kwak have a different approach to this in their treatment of filtering in non os dacs, but what is the difference in sound between a perfect square wave response, higher order Bessel and a phase shift (distorted) low order Butterworth. Maybe I should just build them both and tell you!!

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20th September 2003, 02:21 PM	#2
bknauss diyAudio Member Join Date: Jul 2002 Location: Gaithersburg, MD	Zodiac, I know you are looking for a passive filter, but I know of an active design using only op amps and resistors. Give me an email if interested. bknauss@eudoramail.com

20th September 2003, 05:13 PM	#3
advance diyAudio Member Join Date: Aug 2003 Location: Schwyz	This link might help.... http://www.filter-solutions.com/passive.html#allpass advance

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