MikeGinIllinois Posted August 3, 2013 Share Posted August 3, 2013 Hi, everyone. I've got a Harman Kardon AVR 7300 in very good working order. I recently ordered a cable that has a 3.5 mm male on one end which I plug into my laptop's speaker output and, on the other end, two RCA males which I plugged into VID 2 on the HK. As soon as I plug the cable in my Cornwalls start to Hummmmmmm. It doesn't stop. I don't have this problem with the optical sound output from my DVD player or with my ROKU Internet TV unit. I have experienced this when I tried to plug in my VCR via a long run of RCA ended audio cable. Is there something about cheap RCA cables that picks up hum? Should RCA cables be "shielded?" I'm not sure what that means. Is this something to do with grounding? Thanks a lot! Mike Gallery Crystal Lake, IL Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted August 3, 2013 Share Posted August 3, 2013 Sounds like a ground loop issue. Is your laptop being powered by AC when you experience this or is it also during Battery use? If AC powered only, is it pluged into the same ac outlet as the rest of the system or from a different ac outlet? If from a distant outlet try plugging into the systems's ac outlet temporarly to see if the hum is eliminated or reduced. miketn Quote Link to comment Share on other sites More sharing options...
MikeGinIllinois Posted August 3, 2013 Author Share Posted August 3, 2013 I looked it up and found that it might be I need a ground loop isolator. I'm going to buy one at Radio Shack today. The problem occurs whether I have the laptop plugged into the power adaptor or running on batteries alone. I'll let you know if the ground loop isolator solves the probem. Thanks, miketn! Mike Gallery Quote Link to comment Share on other sites More sharing options...
MikeGinIllinois Posted August 3, 2013 Author Share Posted August 3, 2013 The ground loop isolator resolved the problem just fine. [] According to the explanation on the back of the Radio Shack Ground Fault Isolator ($20.00) "multiple grounding points occur in a vehicle when an amplifier is mounted in the trunk and the main stereo is in the dash. These multiple grounding paints can let current flow through the shielding of the audio connection cables which results in noise." In my case there must be a different grounding point for the laptop and the amplifier, I guess? Can someone explain this? Thank you. Mike Gallery Quote Link to comment Share on other sites More sharing options...
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