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Old 19th July 2008, 12:47 AM   #1
gregorx is offline gregorx  United States
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Default Simple Line level buffer/active crossover?

Hi All,
I am listening more and more to music at my computer. I know I know.. : )
I bought an external DAC (DAC707) that really made this bearable. So using the opticial out of my PC I go to the DAC and from the DAC I would like to go a 2.1 system. I have a pair of full range speakers that I made from 3.5 tang band drivers a few years ago and I have an unbuffered stereo noninverted 3875 gainclone ready to power them.

I think I just need a little preamp/buffer that would take RCA line level from the DAC and crossover low end to powered woofer/subwoofer and most of the signal to my tang bands. I think I could make a couple of active filters using OP2134s or something but if someone had something all made up ideally with a PCB that would be great. Sorry if this is a common question I did search a while for it first.

Any ideas?
gregorx
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Old 19th July 2008, 03:33 AM   #2
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Old 19th July 2008, 07:26 PM   #3
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I have been working on the same problem - see the thread I just started:

Subwoofer Crossover - please critique
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Old 19th July 2008, 08:01 PM   #4
gregorx is offline gregorx  United States
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Thanks guys,
What about something like the attached schematic or 12db version of same?

gx
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Old 19th July 2008, 08:15 PM   #5
gregorx is offline gregorx  United States
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oops I posed an older version. here is the current version just with different values for the caps.

I will post the curves next.
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Old 19th July 2008, 08:17 PM   #6
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You might find the slopes a bit too shallow on the sub and voices bleed through with that.

I've a sub-woofer controller project on my website if you want to take a look. www.readresearch.co.uk
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Old 19th July 2008, 08:18 PM   #7
gregorx is offline gregorx  United States
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Here is the simulation for on channel of the second schematic I posted, sorry it is shifted up 3db.
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Old 19th July 2008, 08:29 PM   #8
gregorx is offline gregorx  United States
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Quote:
Originally posted by richie00boy
You might find the slopes a bit too shallow on the sub and voices bleed through with that.

I've a sub-woofer controller project on my website if you want to take a look. www.readresearch.co.uk
Thanks Richie,
Nice site and projects. When you say voices you mean that I will hurt my left/right separation? What are the slopes like for your subwoofer controller?
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Old 19th July 2008, 09:27 PM   #9
gregorx is offline gregorx  United States
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Default 12dB Version

Well here is a 12dB version for discussion. It includes the slopes.
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Old 20th July 2008, 10:35 AM   #10
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The problem with passive is that it's totally dependent on the amp input impedance. Unfortunately the diagram above won't work once you connect it to any typical amp as it will load down the filters totally screwing them up.

The slope on my controller is 12dB/oct followed by an additional upper 12dB/oct, as annotated on the schematic.

Thanks for the kind comment.
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