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Old 9th October 2003, 08:55 AM   #1
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Question Isolating L and R grounds???

Just a quick question about building a stereo amplifier. When building the circuit is it ok to tie both the left channel and the right channel grounds to the main AGND for the circuit or should the two channels remain isolated from eachother? i.e. seperate grounds for the left channel and right channel. Will there be any noise or cross-talk picked up by tieing them together?

I know this seams like kindof a dumb question but I am going to use the LM4765 stereo amp for a pair of surround speakers in my system and this chip has a seperate ground pin for each channel and this makes me wonder if each channel needs to be kept seperate.

Any info that can be provided will be greatly appreciated.

thanks,
Shawn
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Old 25th October 2003, 09:58 AM   #2
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i beleive national has some relevent info in the datasheet. basically if there is "signifigant" current flowing in a common ground path, a signal will be created at both amplifers. so there will be some crosstalk. star grounding gives each signal and ect... its own ground return wire so that signals do not have to travel across the same resistance and thus become superimposed at the inputs of the amplifer. note that the effect may also be reduced by changing the size of the wire to a larger gauge as this should reduced the voltage drop across the wire.

it should be easy to allow the amplifer to take either method.
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Old 21st February 2006, 06:50 PM   #3
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Default Isolated Grounds

I seem to remember a reader's letter to an old issue of Audio Amateur (~1990) regarding "Dual-Mono Grounding". As I recall, the reader exclaimed that once he separated the L & R grounds, it opened up a whole new clarity for "spatial separation", or something like that.

Anywho, I think it is worth trying. This would entail separate power supplies for each channel.

Steve
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Old 22nd February 2006, 09:50 AM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
is there only one ground from each chip amp?

What is AGND?
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Old 22nd February 2006, 10:36 AM   #5
Nordic is offline Nordic  South Africa
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The amp I'm rebuildign at the moment has common grounds on the inputs, and split grounds on the outputs.

Thought it was weird...
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Old 13th June 2006, 04:50 PM   #6
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Nordic-

Did you ever do anything with the '4765s? pc boards? Pics?
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