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-   -   Bridged OPA541 amp humming (http://www.diyaudio.com/forums/chip-amps/54269-bridged-opa541-amp-humming.html)

kinser 26th March 2005 06:44 PM

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

Russ White 26th March 2005 07:45 PM

I think I would isolate the chips.

kinser 26th March 2005 08:05 PM

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

Russ White 26th March 2005 10:12 PM

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.

kinser 26th March 2005 10:14 PM

Hey Russ White,
Thanx anyway.. I'll go tmrw to get some mica or somthing...

Thanks,
Kinser


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