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Old 16th February 2006, 01:14 PM   #1
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Join Date: Sep 2004
Location: paris
Default need big help with LM1876 design

hello everyone

i have a problem with a LM1876 stereo chip amp design.

i use one chip per speaker in a bi-amp configuration, with an 24db linkwitz active crossover. The two amps and the filter are powered by the same power supply, excepting that there is a regulator stage for the filter.

also there is only one ground for the filter and the chipamps, the power supply ground is connected to the amps and op amps, and the ground for the signal in is also connected on that ground. i don't know if it's clear.

the two section of each mono side of the filter (LP+HP) goes into an lm1876 chip. When i connect one of the to speaker drivers all is ok, but when i connect the boomer + the tweeter, there is horrible distortion. When there is no sound, if i push the boomer's membrane, there are sort of loud sound artifacts.
although if i plug the tweeter into the left section and the boomer into the right section, using only a side of each chips, it works ok.

I guess it is a grounding problem, but i don't know how to resolve it, please help me !
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Old 16th February 2006, 07:24 PM   #2
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Join Date: Sep 2004
Location: paris
please help me, should i make the supplies ground and the signal ground separate ?
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Old 16th February 2006, 07:52 PM   #3
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Join Date: Dec 2002
Location: Calgary, Alberta
What you are describing does not sound like a ground loop at all. If all your grounds were connected, even with a ground loop, it would not account for what you are describing. It sounds like you have not wired it properly or some component is faulty.

Your few words of text are not enough to troubleshoot from. How about a schematic?
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. Bertrand Russell
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