Audio Systems: Humming sound, earphone jack, rca cd

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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