Cable Line Induced Speaker Hum

Discussion in 'Archived Threads 2001-2004' started by John Nielsen, Mar 12, 2003.

  1. John Nielsen

    John Nielsen Stunt Coordinator

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    I recently installed a new power amp for my front speakers and ever since I had done so, I get a very low hum from the speakers when the amp is turned on. I re-ran all of my speaker/power wires with no difference. I finally unplugged the cable TV wire from the wall and the hum stopped. The moment I plug it back in, I get the hum again. Any suggestions on how to stop this?
     
  2. Chris A H

    Chris A H Stunt Coordinator

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    Look here for some ideas.
     
  3. John Nielsen

    John Nielsen Stunt Coordinator

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    Thanks, I'll give it a try.
     
  4. sam_canavo

    sam_canavo Stunt Coordinator

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    Funny you should mention this I have the same problem
    when I plug in the the cables from my computer soundcard
    to the receiver and nailed it down to cable as well.
    Hope we can get this solved, cheaply.
     
  5. John Nielsen

    John Nielsen Stunt Coordinator

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    Worked Great. Thanks!!!

    Edit: Sam, the Radio Shack method should work for you too.
     
  6. sam_canavo

    sam_canavo Stunt Coordinator

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    Tried that didn't work cable guy coming tommorrow.
     
  7. John Nielsen

    John Nielsen Stunt Coordinator

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  8. JeremyFr

    JeremyFr Supporting Actor

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    I've had this same problem when I used to have my Computer hooked up to my system. It seems to only do it if you add in a grounded piece of equipment, i.e. anything with a 3 prong plug. I too called and had a tech come out theres nothing they can really do aside from possibly trying to reground the cable to the house ground point but this does not always work either.
     
  9. sam_canavo

    sam_canavo Stunt Coordinator

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    The cable guy was here and went to the main box, I now
    live in apt. He said it didn't seem to be grounded properly
    but didn't know if he could fix it and was going to call
    someone higher up.
    He suggested I get one of those power bars with coax connections and wham-o for 9.95 the hum is gone.
    I am probably the only one in building with all this
    equipment so no one else would notice.
    Funny thing is it only hummed when input was switched to CD
    where soundcard is plugged in.
    Jeremy any comments on this?
     
  10. EricaK

    EricaK Auditioning

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    Something to add here:

    The balun transformer (Radio Shack) method may not work too well if you have digital cable. I tried it on mine, and got significant breakup/pixiliation on some of the channels.

    Jensen makes a (supposedly) digital cable compatible RF transformer, the VRD-1FF, which I've ordered but not tried yet. I'll report on how it does when it comes in.
     
  11. sam_canavo

    sam_canavo Stunt Coordinator

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    I didn't seem to have trouble with digital cable box only
    computer output. What problems are you having? No RF transformer worked for me and was inserting it where cable enters apt.
     
  12. Bill Kane

    Bill Kane Screenwriter

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    Sam,

    Perhaps you are OK for now. Ideally, the cabletv entering a building should be bonded to the same earth ground used by the building's main electrical service. Since you live in an apartment building, over time who knows how the original bond has held up, split repeatedly and what not.

    My guess is that by inserting a surge protector with F-connecters for a coax cable, plugged into the same wiring used by your HT equipment, you have electrically grounded that coax, thus removing the ground loop voltage difference, and hum.

    I usually recommend this try-out first before buying the inline devices. Ya never know. Seems to work for you, now, right?
     
  13. EricaK

    EricaK Auditioning

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    Sam-

    I am having severe 60 hertz (ground loop) audio hum and crawling horizontal bars on the video. Goes away completely when I use the baluns or the first Jensen RF isolator, but with too much signal degradation for the digital cable to hold up. I'm hoping the second isolator will do the trick.
     
  14. JeremyFr

    JeremyFr Supporting Actor

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    EricaK I had the same problem I finally just went out and bought a DVD player instead of using my Computer and bam it was fixed hehe. But yes typically this happens because the cable is not grounded at the same point the building/house is and in the past this was not an issue obviously but now as HT becomes bigger and bigger and more people are hooking up grounded gear with the Cable box's or even standard cable with now box it produces this phenomena. I would probably have to suggest that you get something inline with the cable to break the ground loop but dont do it with something that will degrade the signal. Remember Digital Cable goes up to 1ghz on the cable so using that transformer idea would probably degrade the signal to much for it to work correctly.
     

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