Audio Systems/Humming sound

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Expert: - 5/12/2009


Question
I get a humming sound (60 cycle hum?) from my amp when I listen to music thru the amp from my laptop. My amp is a Pioneer VSX-74TXVi. I run a cord from the earphone jack on my laptop thru an adapter cord to the rca CD input jacks on the amp. How can I cure this? Thanks

Answer
It is probably a grounding problem between the laptop and amp.  If either of the units have a non-polarized plug try reversing the plug in the socket.

Does the hum go away when the power cord to the laptop is disconnected?  If so, it is for sure a grounding problem and will require something to either isolate the two grounds or grounding corrections.

You might experiment as above in search of the solution; in the worst case you may have to add an isolation transformer between the PC and the amp.  You can google shop for these items or buy them from an electronics parts shop.  Radio Shack used to carry them; don't know if they still do or not.


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Cleggsan

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Audio Design Engineer; systems, loudspeakers, cd/dvd players, etc. I am knowledgeable in all high end audio equipment and installations. MAKE SURE YOU GIVE A MAKE AND MODEL NUMBER AND CAR IF IT IS AN AUTO QUESTION. Note: I am getting some who ask good questions that take a lot of time to research but then the questioner fails to read the answer. Please don't ask questions unless you are seriously looking for an answer. If you find an answer to your question otherwise then let me know with your reply. Thank you.

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Have been associated with audio design, standards, testing and component systems for over 40 years.

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Life Fellow Member of Audio Engineering Society Life Senior Member of Institute of Electronic and Electrical Engineers

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Review technical manuscripts for IEEE Spectrum Write occasionally for high-end audio publications

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BSEE/MSCS/MBA

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Past Employee/advisor to several well known audio products manufacturers

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