VCR, not cable causing hum in amp???

Discussion in 'Archived Threads 2001-2004' started by Philip_T, Jul 22, 2002.

  1. Philip_T

    Philip_T Supporting Actor

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    Well, I finally got my Parasound 885 and hooked it up anticipating some improved sound for my Denon2802 pushing Klipsch RF3-II's (f), RFC3-II (c), some Polk bookshelf rears and a def tech sub. I turned it on and put the hammer down. WOW! This was the sound I was hoping for all along. Much improved soundstage, background tracks aren't drowning out, cleaner, more powerful bass, etc. I was in heaven, until I went to change CD's. Then I heard the imfamous "hum" that I later found out is much documented here at HTF. After finding out that the main cause for this is the improperly grounded cable line, I rushed home after work, turned on the amp, unplugged the cable from the wall, and silence. OK, I anticipated this and had my handy grounding block, went to my cable box outside, but there was already one there. So I tightened the screws and tried again, no luck. Next, I removed the rca audio outputs from my vcr, silence. Hmmm, so I tried them in my tv audio out and the hum did not return. So my question is this, is there any way to cure the outputs from the vcr going into the Denon from humming? I currently have my cable coaxial coming from the wall into my vcr input, then coaxial out of vcr into the tv, with the rca audio out from tv to the Denon Video 1 audio input. TV doesn't sound as good, but no hum. PLII definately sounds weaker watching tv or vhs. DVD's sound fine. This is a temp fix that works for now, but I would like to run cable audio out from my vcr someday. I have the cable guy coming tomorrow to look at the cable box hookup, but it looks like that may not be the problem and I dont want to have to pay the service charge if he's not needed. Any advice would be greatly appreciated. BTW, receiver, amp, vcr, tv and sub are plugged into the same power strip, and I've been convinced not to try the ground cheater method either.
     
  2. Geoff S

    Geoff S Stunt Coordinator

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    I don't know if this helps you, but almost always when I have my Denon 4802 (or any recevier I've used for that matter) connected to an analog source that isn't playing (the receiver's input set for that source), especially on long cable runs I get some static noise. When Digital I get no noise at all.
     
  3. Marvin

    Marvin Screenwriter

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    Philip, I have the exact same situation as you; same amp, same hum even though there already is a cable grounding block outside. I tried a ground loop breaker: http://www.hometech.com/video/atten.html#dc
    but this didn't seem to help at all. This one was only about $10 or so with the shipping so I figured it was worth a shot. I've seen other such devices on the web for $50-100.
    Right now I'm using a cheater plug, which I'd like to get rid of. I'd be interested in finding out if the cable guy, or anyone else, is able to help you at all.
    By the way, in my case, I get the hum/static when the receiver is set to CD and DVD, i.e. a digital source. It goes away when I set it to tape - the opposite of what Geoff found.
     
  4. Philip_T

    Philip_T Supporting Actor

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    Well, the cable guy came and went and needless to say, I still have my hum.[​IMG] All he did was take the coax out of the vcr and plug it into the tv and said, "see, tv not making hum, its not the cable". I about went through the roof. Regardless, he spoke very little english and we couldn't understand each other, but in his infinite wisdom, he thought it was my Denon. He didnt even check the grounding outside. I pray theres no service charge for that.
    Marvin, I checked all my input selections and it hums on all of em, even tape. Back to the drawing board for now. Ive heard of a 75-300-75 trick that I may try later today. I'll let you know.
     
  5. Wayne A. Pflughaupt

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    Marvin,

     
  6. Kevin Deacon

    Kevin Deacon Second Unit

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    I have the same problem with hum. I had the cable guy run the ground to the inside of the electrical panel and ground it there. This helped very little so I am now using the Rat Shack 75-300-75 trick at the expense of having ghosts on certain cable channels, but the hum is gone.
     
  7. Philip_T

    Philip_T Supporting Actor

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    Wayne,
    Thanks for your response and great info. I went and checked all the screws again on the grounding wire, both at the cable box and on my water main, both were hunkered down. Wire doesn't appear that old, house built in 1993. Tried your advice on removing incoming rg6 at ground loop and hum disapated a little, but was still there.
    Im wondering if a ground loop isolator might help?
    Regarding the tv audio, yes, I had the audio running into the receiver and the tv speakers down all the way, no hum from the amp, but poor audio quality in general (its just a cheap 27" Sanyo).
    Sub is plugged into same surge protector as amp/rec/tv/vcr. Again, thanks for all your tips, its definately help my narrow it down.

    Regards,
    Phil
     
  8. Marvin

    Marvin Screenwriter

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  9. Philip_T

    Philip_T Supporting Actor

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    Problem Solved![​IMG]
    Went to Rat Shak and picked up a ground-loop isolator here and ran it out from vcr audio out to receiver and blessed silence. Well, at least until I ran DMB at -15db. [​IMG]
    Thanks for all of your input. You may want to give one of these a try Marvin. I cant say it will cure your hum, but it worked for my situation.
    Regards,
    Phil
     
  10. Marvin

    Marvin Screenwriter

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    OK, thanks Philip. I'll give it a try. I had seen that before but I thought it was only for use in cars. I had thought you needed something in the cable/coax path (i.e. with RF connectors) rather than the A/V path.
     
  11. Wayne A. Pflughaupt

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    Philip,

     
  12. Vlad D

    Vlad D Screenwriter

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    Philip,

    I also had the same problem. Same amp, same receiver. Hum was also caused by VCR. I solved the problem by just disconnecting my VCR from my receiver since I don't use it that much. But I think I'll give your solution a try.
     
  13. Marvin

    Marvin Screenwriter

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  14. Wayne A. Pflughaupt

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    Marvin,
    I’m not familiar with this device, but it probably works like the dual transformers that Kevin used. In any event, you have already said it didn’t help, so it really is moot. You might try Kevin’s trick using two 300- to 75-ohm transformers instead. I’ve also heard that one of the more expensive units, namely from Mondial (sp?), will work where the dual transformers fail.
    A couple of other things:
    • Try plugging the sub into the same outlet as the rest of the equipment, as I noted in the earlier post.
    • Make sure no component with the cable feed attached (i.e., a cable box or VCR) is sitting directly on top of the receiver or amp.
    By the way, your cable signal isn’t split many times – the booster may not be needed.
    Regards,
    Wayne A. Pflughaupt
     
  15. Marvin

    Marvin Screenwriter

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  16. Marvin

    Marvin Screenwriter

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    Just an update in case anyone's keeping score: detaching the VCR audio wires (and also a video cable that I was using for the on-screen display) did NOT take away the hum so I guess there's no point in getting that device that worked for Philip.

    Is there anything else I should try?
     
  17. Wayne A. Pflughaupt

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    Marvin,

    If I’m up to date, you still haven’t tried the back-to-back 75- to 300-ohm transformers.

    Also, did you disconnect the cable company’s feed from the grounding block, as I noted in Post #5?

    Regards,
    Wayne A. Pflughaupt
     
  18. Marvin

    Marvin Screenwriter

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    Wayne,
    I tried that device I mentioned http://www.hometech.com/video/atten.html#dc which I assume is the same as a 75-300 transformer. Right?
    No, I haven't disconnected the cable company's feed from outside so I guess I'll try that next - assuming I can (the grounding block was painted over the last time I had my house painted).
    I've previously tried to tighten all the screws connecting the ground wire but wasn't able to make them any tighter.
    Thanks
     
  19. Wayne A. Pflughaupt

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  20. Marvin

    Marvin Screenwriter

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    Wayne,
    There are several items on that page. The one I bought and tried was the 63400 ground breaker. I think you're referring to the 20300 DC blocker.
     

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