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Need help eliminating strange buzz on HT system!


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#1 of 7 BTaudio

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Posted February 15 2010 - 04:56 PM

I am running an Onkyo TX-SR605 receiver with Onkyo 5.1 surround sound speakers.  

When I plug in my MacBook Pro via an RCA to 1/8" cable, the audio has a strange buzzing noise that is accentuated when I scroll up or down on web pages, open hard drive windows, etc.

20 second Sample of buzz:
http://www.filedropper.com/20100215220919 

I took in my MacBook Pro to the Apple store, and they said they could not reproduce the buzz and that my audio card/port appeared to be working properly.

However, when I plug in my iPhone, or my wife's Macbook, there is no buzz and the audio works flawlessly.  Also, my dvd player works fine without a buzz...

Any suggestions on how to get rid of this buzz??  Is the guy at the apple store full of it?

Any help is greatly appreciated!  Thanks!


#2 of 7 chuckg

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Posted February 18 2010 - 08:48 AM

Does the buzz happen only when the Mac is using wall power?  Rather, does the buzz go away when running on battery?

If so, the quickest fix is a three-prong to two-prong power plug adaptor.  I have "ground loop" problems like this all the time here at work when people bring in a laptop for presentations, and the little cheater plug solves it every time.
--ignore the man behind the curtain

#3 of 7 Phil A

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Posted February 18 2010 - 11:08 AM

 Defeating the ground is a safety issue.  It could be the cable,  If it stops when you put a USB device like and iPhone, why not just get a USB thumb drive and leave it in

#4 of 7 chuckg

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Posted February 22 2010 - 02:59 AM

" Defeating the ground is a safety issue."

Not true.

Have a look at the numerous items that do not have a ground pin on the plug: electric drills, lighting equipment, quite a lot of electronics, kitchen gadgets, and on and on.  The neutral wire in the power cord is grounded, the extra ground is there for the "just in case" moments, such as somebody cuts the neutral wire.  Lifting the ground is a valid solution, and until manufacturers learn to separate signal ground from safety ground, I'll be buying adaptors.
--ignore the man behind the curtain

#5 of 7 Phil A

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Posted February 22 2010 - 10:29 AM

 I don't think so  - http://www.straightd...uitar-dangerous

#6 of 7 Joseph DeMartino

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Posted February 23 2010 - 04:53 AM

Defeating the ground IS a safety issue.  Devices that have three prong power cords have them for a REASON.  Having said that, properly using a 3-prong to 2-prong adapter doesn't constitute "defeating the ground", so everybody is partially right.  As long as you install the adapter according to directions and screw the ground wire in place, you're fine.  Cut the ground pin off a 3-prong plug to get it to fit a 2-prong outlet - or use a 2-prong adapter without screwing down the ground wire - and you're asking for trouble. 

Regards,

Joe

#7 of 7 chuckg

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Posted February 23 2010 - 05:24 AM

Using the adaptor "properly" does not disconnect the ground !  and that ground is the source of the hum in 99% of cases.

from the same article:
Another important safety feature found on much equipment these days is the polarized plug. This is a two-bladed plug with one blade wider than the other so that it will only fit into the outlet one way. The purpose of this type of plug is to keep the "hot" side of the AC supply as far from the user as possible.


Two prong safety.  Again, have a look at the numerous items that do not have a third wire.
--ignore the man behind the curtain




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