line level high pass filter

rbrockman · 4th December 2008, 10:37 AM

I am looking for some suggestions regarding a line level high pass filter for main speakers. I don't mind building a circuit as long as it is a good or better than something I can buy reasonably.

I would like to be able to filter out <~60hz signals from reaching the mains. If possible I'd like to be able to adjust this freq. I believe a 2nd order filter is what I'm looking for.

I am using a digital source -> DAC -> Amp -> Main Speakers

1) Should this be passive or active?
2) If there is consensus on #1, is there a recommendation for a high quality filter?

Thanks for any feedback.

SY · 4th December 2008, 10:59 AM

At frequencies that low, I think that active is the way to go. You can do it pretty simply (Sallen-Key filter made from opamps) or you can get a bit more sophisticated (for example, the Acheron crossover shown on my website). Either approach will well outperform a large, clunky inductor and equally large, clunky capacitors.

raudio1969 · 13th December 2008, 03:21 AM

How much attenuation is needed at 60Hz? Here is a circuit which will give -12.4dB at 60Hz. It was generated by Microchip's FilterLab software.

http://www.microchip.com/stellent/id...cName=en010007

planet10 · 13th December 2008, 05:21 AM

The high pass of a PLLXO coule be used. 2nd order gets kind of droppy and if your amp has a low input impedance could be a no go... (i'd suggest 50k or higher input impedance, and if that low make R2' infinite and the cable short).

http://t-linespeakers.org/tech/filters/passiveHLxo.html

If the input impedance is an issue and you still want to approach it this way, you can sandwich the PLLXO between 2 buffers. I have a dual 9V battery powered one for one of my speakers, but it could be done with jfet beffers (like in Nelson's B1 or cathode followers (don't forget the CCS)

SY's XO is also very interesting -- i'm no big fan of SK... I'm happy he did the groundwork for this so the rest of us don't have to. Thanx SY.

dave

4th December 2008, 10:59 AM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	At frequencies that low, I think that active is the way to go. You can do it pretty simply (Sallen-Key filter made from opamps) or you can get a bit more sophisticated (for example, the Acheron crossover shown on my website). Either approach will well outperform a large, clunky inductor and equally large, clunky capacitors. __________________ “There are no greater liars in the world than quacks, except for their patients.” - Benjamin Franklin

13th December 2008, 05:21 AM	#4
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	The high pass of a PLLXO coule be used. 2nd order gets kind of droppy and if your amp has a low input impedance could be a no go... (i'd suggest 50k or higher input impedance, and if that low make R2' infinite and the cable short). http://t-linespeakers.org/tech/filters/passiveHLxo.html If the input impedance is an issue and you still want to approach it this way, you can sandwich the PLLXO between 2 buffers. I have a dual 9V battery powered one for one of my speakers, but it could be done with jfet beffers (like in Nelson's B1 or cathode followers (don't forget the CCS) SY's XO is also very interesting -- i'm no big fan of SK... I'm happy he did the groundwork for this so the rest of us don't have to. Thanx SY. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

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4th December 2008, 10:37 AM	#1
rbrockman diyAudio Member Join Date: Aug 2007	line level high pass filter I am looking for some suggestions regarding a line level high pass filter for main speakers. I don't mind building a circuit as long as it is a good or better than something I can buy reasonably. I would like to be able to filter out <~60hz signals from reaching the mains. If possible I'd like to be able to adjust this freq. I believe a 2nd order filter is what I'm looking for. I am using a digital source -> DAC -> Amp -> Main Speakers 1) Should this be passive or active? 2) If there is consensus on #1, is there a recommendation for a high quality filter? Thanks for any feedback.

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