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Old 2nd March 2007, 04:07 PM   #1
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Default 2 LM3876 plus 1 LM3886 using Linkwitz-Riley crossover

Hello I've just built my first gainclone using 2 LM3876 from 2 50W kits from Jaycar here in Australia. I have to say they sound great, but they seem to "bright" and I want more bass.

I have an additional LM3886 amp that I want to use to power a 10" subwoofer, in turn making a 2+1 system for my lounge room.

I want to use Rod Elliott's Project 09 (24 dB/Octave 2-WAY Linkwitz-Riley Electronic Crossover) as my pre-amp filtering, which results in mid-high pass powering the 2 satellites and the low pass powering the sub.

My question is how can I mix the left and right low pass channels into the sub amplifier? Is it as easy as joining the two outputs from the low pass section in Project 09?

Cheers.
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Old 3rd March 2007, 10:03 PM   #2
sek is offline sek  Germany
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You can peek into Projects 48 or 71 to see how to 'sum' the input before the low pass filter.

For your satellites, you'll need one high pass for the left channel and one for the right channel.
The subwoofer mono sum can be derived directly from the stereo input, no need to waste the space and money for two identical low passes. IC U1A in P48 (or P71) shows how to do it. Then connect one of P09's low passes behind such a summing buffer.

You might also want to read Siegfried Linkwitz's original articles, some of them also show how to design a 2.1 crossover.

Cheers.
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Old 4th March 2007, 01:47 AM   #3
gofar99 is offline gofar99  United States
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Greetings, Usually I wouldn't mention a particular company, but this info might be of help to you. I just completed a similar arrangement and for the crossover used a kit from Marchand electronics (New York USA). I just stumbled on them by accident. The kit was pretty cheap for a pair of xovers (about $65US) and the quality was excellent - glass boards etc. It is a 24 db high and low, the freq can be adjused by changing 4 identical resistors on a dip header. They include one set at the freq of your choice. Mine came with Burr Brown ICs. Very quiet and works super.

Good listening
Bruce
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