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Old 26th March 2005, 06:44 PM   #1
kinser is offline kinser  Israel
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Default Bridged OPA541 amp humming

Hi all,

I built about 2 months ago a powered subwoofer using 2 OPA541's bridged, now it had some problems and i fixed them today, but still have the humm... I have checked for any ground loops but didnt find any, but then while the amp was on, and playing music I touched the heat sink and the humm dissapeard! but, but... the OPA's share the same heatsink and are not isolated, because the tab is the -Vs, but when I check to see if there is any kind of connection between the tab and the -Vs pin (on the data sheet it sais there is), there is no connection.

So what do I do?? do I ground the heatsink? well I cant because the chips are not isolated and the -Vs should be going through the tabs, so again, what do I do?

Thanks,
Kinser
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Old 26th March 2005, 07:45 PM   #2
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I think I would isolate the chips.
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Old 26th March 2005, 08:05 PM   #3
kinser is offline kinser  Israel
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Russ White,
Thanx, I will do that, but i would like to know why is there a hum, because both tabs are V-

Thanks,
Kinser
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Old 26th March 2005, 10:12 PM   #4
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I am not sure, but I have seen the same sort of behaviour out of LM4780s and that solved my problem. Wish I could tell you why.
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Old 26th March 2005, 10:14 PM   #5
kinser is offline kinser  Israel
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Hey Russ White,
Thanx anyway.. I'll go tmrw to get some mica or somthing...

Thanks,
Kinser
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