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Old 27th May 2005, 02:46 PM   #1
croire is offline croire  France
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Default lm3886 280watt

i want to build a 280watt with 8 lm3886 ;/channel to make a home cinema

what do you think about this
Click the image to open in full size.

Click the image to open in full size.

R7 are 0.22 ohm
+u and -u are +- 40volt
what can i change in the diagram to improve the ampli

cordially
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Old 27th May 2005, 09:36 PM   #2
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What is the purpose of P1?. I think part of figure 12 is missing,if not, both side s1 and s2 should match( r4,r5 and c1).
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Old 27th May 2005, 10:00 PM   #3
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Volumepot?

I think they have just skipped the feedback part because the schematic would be "blurry" ?
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Old 27th May 2005, 10:09 PM   #4
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If dephaseur is a chip(ie. drv134)that will split the signal,why would two pots be needed. they might add balancing problems.
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Old 28th May 2005, 05:22 AM   #5
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from what i understand, parallel amps need to be closely matched as possible. so they are not driving into each others outputs and causing heat and distortion..

each of the 8 amplifiers has 3 capacitors (1 electrolytic even) and 4 resistors affecting the feedback loop.any variation will cause difference in the outputs and distortion.

try and match them as well as you can.

I also wonder what may happen if spike protection was to kick in at different times on the different chips.
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Old 28th May 2005, 05:31 AM   #6
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I was wondering why you would need to repeat the zobel network R3/C3 for each chip.

Also, isn't bridging into 4 ohms a problem.
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Old 28th May 2005, 06:41 AM   #7
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Maybe so you can have each zobel right at the pins of each chip for best effect at HF.
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Old 28th May 2005, 03:48 PM   #8
croire is offline croire  France
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the diagram of the balanced preamp
Click the image to open in full size.

Click the image to open in full size.

so i won t use this preamp , i will use the dvr134 or other

in the diagram of the ampli lm3886 i use 1% resistors, silvermica 1% for the10pf=c1, c3=MKP 1%, and C5 C6=1000f
we can use c1 10pf to 40 pf what is the best for c1

cordially
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