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Subwoofer/Cable Hum


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#1 of 2 Shane Clays

Shane Clays

    Auditioning

  • 1 posts
  • Join Date: Apr 29 2004

Posted April 30 2004 - 04:54 AM

All,

I am new to the forum, so forgive me if this has been hashed and re-hashed before, and want to aplogize in advance for what promises to be a long message, but here goes...

I recently added an MTX 15 inch class D sub to my system which also consists of a set of 4 Wharefdale Z3s and the matching center. The entire system is powered by a Technics 5.1 capable reciever (sorry, dont have the model number handy). I used low level line input for the sub. Monster Cable throughout the entire system.

Overall, its not a bad sounding system and everything seemed to be moving along just fine, then I got cable installed (had recently moved and was waiting for the cable installation) and thats where the problems began. When the cable is plugged in, I get a low but loud hum through my subwoofer. The hum increases when I turn the volume up on the sub. I do not get the hum through the rest of my speakers, presumably because the crossovers remove it, but I do get it through the TV speakers.

Now, what I have done to trouble shoot.... first, when I unplug the cable, everything is fine, but when I plug it in, the hum returns. When I unplug the sub with either the power cable OR the low line level input, the hum in the sub and the TV goes away. In other words, if I unplug the sub, cable is cool and if I unplug the cable, sub is cool.

I thought it may be the low level input cable, so I wired in a high level input to the sub and the hum is still present. I also bypassed the reciever and plugged the low level line input directly into the audio out on the cable box and the hum is still there (meaning, I dont think it is in the reciever). I have also completely seperated all of TV cable from all of my audio cable.

Another thing that is odd, is that when I unplug my color component cables from the DVD player to the TV, the hum goes away. This happens because at that point the cable and
the sub have not common connection.

I have also tried grounding the cable jack as well as the sub (wired a ground onto the heat coils of the amp) and still a loud hum. Finally, the other thing that is happening is that when I use my reciver OR just plug in and unplug the sub, it makes a very loud and nasty pop which I am afraid is going to damage the sub if it continues to happen. My guess here is that I have a grounding issue somewhere, but have no idea where to start beyond what I have already done. Any suggestions out there??

TIA,
Shane Clays

#2 of 2 Chris A H

Chris A H

    Stunt Coordinator

  • 172 posts
  • Join Date: May 10 2002

Posted April 30 2004 - 08:15 AM

Ground loops are common and have been discussed here in the past. Try this link for some solutions.