Subwoofer hum

[dgreenbu]

A couple of months ago I had a tech move my whole setup from one room to another. When the system was turned on there was a substantial hum from the sub. He eliminated the hum by inserting a "ground breaker feed-thru surge protector" between the coaxial cable to the Comcast/Infinity X1 DVR-actually an RNG-150. Recently my receiver went down and I bought a used Yamaha RX-X375 to use while waiting for the other unit to be repaired. After setting it up I found the X1 box would not connect to Comcast. Removing the surge protector allowed connection to Comcast but returned the hum to the sub. This is not some slight hum- you can feel the cone vibrating substantially. Removing the HDMI cord from the DVR or unscrewing the coax stop the hum. All units are connected via a Panamax M4300-PM power conditioner. I tried plugging the sub into a different wall socket,but no improvement. HELP!
TIA

 

[TLS Guy]

A couple of months ago I had a tech move my whole setup from one room to another. When the system was turned on there was a substantial hum from the sub. He eliminated the hum by inserting a "ground breaker feed-thru surge protector" between the coaxial cable to the Comcast/Infinity X1 DVR-actually an RNG-150. Recently my receiver went down and I bought a used Yamaha RX-X375 to use while waiting for the other unit to be repaired. After setting it up I found the X1 box would not connect to Comcast. Removing the surge protector allowed connection to Comcast but returned the hum to the sub. This is not some slight hum- you can feel the cone vibrating substantially. Removing the HDMI cord from the DVR or unscrewing the coax stop the hum. All units are connected via a Panamax M4300-PM power conditioner. I tried plugging the sub into a different wall socket,but no improvement. HELP!
TIA

This is a common problem, and called a ground loop. That is a potential between grounds.

As usual, the fault is Comcast's. They have not properly tied their cable ground to your house ground at the panel, as required by code.

Doing that is the proper solution.

I suspect at least one piece of equipment and probably the sub has a ground plug. You will get rid of the hum if you "lift" those ground using one of those three to two pin converter plugs available at Home Depot and just about all hardware stores.

 

[dgreenbu]

This is a common problem, and called a ground loop. That is a potential between grounds.

As usual, the fault is Comcast's. They have not properly tied their cable ground to your house ground at the panel, as required by code.

Doing that is the proper solution.

I suspect at least one piece of equipment and probably the sub has a ground plug. You will get rid of the hum if you "lift" those ground using one of those three to two pin converter plugs available at Home Depot and just about all hardware stores.

Thanks for taking the time to reply. I did see another post in my searches suggesting the same solution so I will try it. Should this be inserted between the sub power cord and the power conditioner or between the power conditioner and the wall outlet. I don't know if it makes a difference but the humming only comes from the sub.

 

[j_garcia]

You should just be able to tell comcast to do it and they should come out and do it free of charge. I had the same issue with them before.

 

[TLS Guy]

Thanks for taking the time to reply. I did see another post in my searches suggesting the same solution so I will try it. Should this be inserted between the sub power cord and the power conditioner or between the power conditioner and the wall outlet. I don't know if it makes a difference but the humming only comes from the sub.

It depends on which units have three pin plugs. I bet only the sub has one. If this is correct then put the ground lifter on the sub.

If you only have one ground, the you will have no hum.

As you had the problem, then either, or neither the outlet ground, or the Comcast ground are true ground. My bet is that the Comcast ground is not true ground. So after you stop the hum, the Comcast ground will be your only ground.

The problem is that Comcast have a lot of idle ignorant installers and I have seen some really bad lash ups left by those guys.

So, I would make Comcast ground their installation properly according to code for your long term solution. However good luck with that, as I would bet you will find it hard to find anybody in Comcast who knows the electrical codes or what a ground loop is.

If you are handy and educate yourself a little, this is something you can do. However Comcast should have made the cable entry in proximity to the panel. Often they don't, as they want to run the shortest cable, which is not proper.

If the Comcast entry point is reasonably close your house ground, then this is easily solved, if not then you will have to try and make Comcast follow code.

The electrician almost certainly followed code, as he has the electrical inspector down the back of his neck.

So, since you have the hum, the Comcast installation is almost certainly not proper.

 

[KEW]

The electrician almost certainly followed code, as he has the electrical inspector down the back of his neck.

Unfortunately, that is not always the case.
Here in Georgia, the budget for inspectors has been largely stagnant over decades despite the steadily increasing growth (especially metro-Atlanta).

 

[dgreenbu]

Thank you all for your input. I went to Home Depot this pm and for $.64 bought a three to two adapter came home, put it on the subwoofer's plug and Voila!!! No more hum. I am so grateful that I don't have to deal with Comcast yet again. If I had run my dental practice the way they run their business I would have failed long before retirement. Fortunately for them and unfortunately for consumers in this area they are the only game in town if you want cable.

 

[TLS Guy]

Thank you all for your input. I went to Home Depot this pm and for $.64 bought a three to two adapter came home, put it on the subwoofer's plug and Voila!!! No more hum. I am so grateful that I don't have to deal with Comcast yet again. If I had run my dental practice the way they run their business I would have failed long before retirement. Fortunately for them and unfortunately for consumers in this area they are the only game in town if you want cable.

You did not quite understand my post. Dentists don't always understand us Docs!

You should get hold of Comcast, as your sub is now grounded via your Comcast cable. This does have some potential to be a safety issue. So you need to have your cable service bonded to your electrical service properly.

 

[lsiberian]

The problem is that Comcast have a lot of idle ignorant installers and I have seen some really bad lash ups left by those guys.

Unfortunately most cable installers get paid so low that's all you get.

 

[dgreenbu]

Okay, I get it. Once more into the breach. I don't know what's worse, trying to cash in credit card air miles or get Comcast to do something correctly.

 

[highfigh]

Okay, I get it. Once more into the breach. I don't know what's worse, trying to cash in credit card air miles or get Comcast to do something correctly.

Call fro Tech Support and ask for a supervisor or Tier Two support. They have people for this, but they usually make it difficult to reach them.

Here's a link regarding this, with info on length of grounding conductor and the link specifically addresses communications cabling.

http://www.dps.ny.gov/gbcs_Comments_Questions_and_Answers.html

This link has more details- look for the sections that apply-
http://www.mikeholt.com/instructor2/img/product/pdf/1049286524toc.pdf

Bottom line- tell Comcast that you know their installation has code violations and that you want it corrected but have the info ready to go if they ask for details. You could always threaten to go to the local inspector and tell them about the violations.

This isn't just a minor problem. It can shorten the life of your equipment and at worst, cause a fire or electrocution.

 

[dgreenbu]

Thanks for the info. Will study up on both sites and call Comcast on Monday.