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Hum FAQ - Page 6

post #151 of 166
LPW

This is not uncommon in my experience, but usually a little trouble shooting solves it.

Quote:


Ground loop is a condition where an unintended connection to ground is made through an interfering electrical conductor. Generally ground loop connection exists when an electrical system is connected through more than one way to the electrical ground

source and an interesting read: link

You may have this condition with your 3 separate circuits. You could try putting them all on one surge supressor to see if it eliminates the problem. It it does, then one by one move them to another circuit, if that's what you desire, until it returns.

If the above doesn't work you can looking into the following.

Does your amp have a grounding terminal? If so, and you have a surge supressor that has a grounding terminal - for your equipment - try grounding your amp to that terminal.

Is your cable or satellite hooked up to your system? If so, you may need to add a ground it at the splitter or add a simple grounding block and ground it to your supressor.

I hope one of these solutions helps.
post #152 of 166
Quote:
Originally Posted by pgwalsh View Post

LPW

This is not uncommon in my experience, but usually a little trouble shooting solves it.


source and an interesting read: link

You may have this condition with your 3 separate circuits. You could try putting them all on one surge supressor to see if it eliminates the problem. It it does, then one by one move them to another circuit, if that's what you desire, until it returns.

If the above doesn't work you can looking into the following.

Does your amp have a grounding terminal? If so, and you have a surge supressor that has a grounding terminal - for your equipment - try grounding your amp to that terminal.

Is your cable or satellite hooked up to your system? If so, you may need to add a ground it at the splitter or add a simple grounding block and ground it to your supressor.

I hope one of these solutions helps.

Thanks for your reply! I did some more troubleshooting tonight and found:

1) If I disconnect the coax cable going from my splitter to the wall plate where my cable box is connected, the hum is reduced considerably.

2) I have a 30 ft HDMI cable run in the ceiling connecting my projector to my receiver and when I unplug the HDMI to the receiver, this also reduces the hum, albeit only slightly. I wonder whether I ran this cable too close to the coax cable in the ceilng. It's a Blue Jeans HDMI cable recommended specifically for long runs.

3) When I have my HTPC turned on, I get terrible static sound through the speakers that I'm driving with the external amp as well as through the subwoofer. The static sound is much more annoying than even the ground loop hum! When I unplug the HDMI cable going from my HTPC to my receiver, the static sounds disappear. I'm using a monoprice HDMI cable.

All signs pointing to a ground loop problem? I also find that plugging the external amp to a circuit different from the receiver reduces the hum. I did try plugging both the receiver and amp into a power conditioner, but that didn't solve the hum. Unfortunately, my new 3-channel amp does not have a ground lift switch like my 2-channel amp and switching it on eliminates the hum when I use the 2-channel amp in this system.

What do you recommend I try next? I do remember that my cable company used a splitter on the outside cable box because they ran one coax into my basement and a 2nd one to the upstairs bedroom. Does this outside splitter affect things?

Thanks very much for your help!
post #153 of 166
Quote:
Originally Posted by lpw View Post

Thanks for your reply! I did some more troubleshooting tonight and found:

1) If I disconnect the coax cable going from my splitter to the wall plate where my cable box is connected, the hum is reduced considerably.

2) I have a 30 ft HDMI cable run in the ceiling connecting my projector to my receiver and when I unplug the HDMI to the receiver, this also reduces the hum, albeit only slightly. I wonder whether I ran this cable too close to the coax cable in the ceilng. It's a Blue Jeans HDMI cable recommended specifically for long runs.

3) When I have my HTPC turned on, I get terrible static sound through the speakers that I'm driving with the external amp as well as through the subwoofer. The static sound is much more annoying than even the ground loop hum! When I unplug the HDMI cable going from my HTPC to my receiver, the static sounds disappear. I'm using a monoprice HDMI cable.

All signs pointing to a ground loop problem? I also find that plugging the external amp to a circuit different from the receiver reduces the hum. Unfortunately, my new 3-channel amp does not have a ground lift switch like my 2-channel amp and switching it on eliminates the hum when I use the 2-channel amp in this system.

What do you recommend I try next? I do remember that my cable company used a splitter on the outside cable box because they ran one coax into my basement and a 2nd one to the upstairs bedroom. Does this outside splitter affect things?

Thanks very much for your help!

Well without a doubt the outside splitter should be grounded, but that may not eliminate your problem with the cable and you ht setup. You could add an inline grounding block like the one I have in this picture



Just do that inside before it got to your tuner or whatever you have it plugged into. Ground that to your surge suppressor. If you're using a cable box, you might avoid this by plugging it into the same circuit as your amp and processor. That's the quickest fix.

I'm running an HDMI cable to my projector which is 35ft and I don't have that issue. I'm gathering you used a cl2 rated cable?

What type of interconnects are you using, balanced or unbalanced. I've heard this can help, but not sure.

I think once you eliminated the main cause you'll start to be able to eliminate the rest. Is your HTPC next to your home theater equipment? If it's near a speaker or magnetic source that's not shielded you'll have issues.
post #154 of 166
Quote:
Originally Posted by pgwalsh View Post

Well without a doubt the outside splitter should be grounded, but that may not eliminate your problem with the cable and you ht setup. You could add an inline grounding block like the one I have in this picture



Just do that inside before it got to your tuner or whatever you have it plugged into. Ground that to your surge suppressor. If you're using a cable box, you might avoid this by plugging it into the same circuit as your amp and processor. That's the quickest fix.

I'm running an HDMI cable to my projector which is 35ft and I don't have that issue. I'm gathering you used a cl2 rated cable?

What type of interconnects are you using, balanced or unbalanced. I've heard this can help, but not sure.

I think once you eliminated the main cause you'll start to be able to eliminate the rest. Is your HTPC next to your home theater equipment? If it's near a speaker or magnetic source that's not shielded you'll have issues.

I took a photo of my outside cable box and traced a black cable (thinner gauge than the coax cables) that leads down and to the left (see photo below). Someone mentioned to me that this is probably the ground wire. Well, this cable ends unterminated and not attached to anything on the outside wall. So, if this is in fact the ground wire, then it's safe to say that I have an ungrounded cable wire??

If this is the case, I'll call my cable provider and see what they say. Where can they ground this wire though? They're not going to have to dig up my driveway to do this, are they?

post #155 of 166
If you have any pole going into the ground, that should work. However, I wouldn't be too concerned about it. Just get a grounding block or splitter and ground it before your equipment - in your house - which you may have to do anyway.

You can do this as well: http://www.ehow.com/how_2076406_grou...able-line.html
Here's a discussion on avsforum: http://www.avsforum.com/avs-vb/showthread.php?t=1128083
post #156 of 166
Quote:
Originally Posted by pgwalsh View Post

If you have any pole going into the ground, that should work. However, I wouldn't be too concerned about it. Just get a grounding block or splitter and ground it before your equipment - in your house - which you may have to do anyway.

You can do this as well: http://www.ehow.com/how_2076406_grou...able-line.html
Here's a discussion on avsforum: http://www.avsforum.com/avs-vb/showthread.php?t=1128083

Thanks for the links. I've been doing a lot of reading and troubleshooting but I haven't found a solution yet. I called my cable company and they sent out a technician who connected a ground wire from the splitter on the outside of the house to a grounding clamp attached to my hydro meter as shown in the pic below:



This actually eliminated the hum I was getting from my two TV's that use a set top box. It did not, however, eliminate the hum and static noise I'm getting from my 2-channel (amp + preamp) and home theater (receiver + amp through receiver's pre-outs).

I then investigated the house ground and found the grounding wire coming out of my electrical panel, which goes up into the ceiling and which I assume comes out at the other end of the room where it is clamped onto the water pipes (see pic below). Now, the coax cable coming into the house feeds into a splitter - should i attach a ground wire to the ground wire coming out of the electrical panel? Would this create the "common ground" and eliminate ground loops?



I also bought a Viewsonic VSIS ground loop isolator (similar to the Jensen VRD-1FF), but it didn't have any effect on the hum.
post #157 of 166
Grounding to a copper pipe is normal in my experience, but I'm not an electrician. I'm just going by what I've commonly seen

Are your components all plugged into the same surge suppressor or outlet?

What about you sub woofer? `

Do any of your components have a grounding lug and are they in use?

When you disconnect your cable/satellite does the hum go away?
post #158 of 166
Quote:
Originally Posted by DogBean View Post
Thanks Dr Spike! Any suggestions for a replacement lamp? Should I go for say, a flourescent lamp?


DogBean,

A candle is your best bet.
post #159 of 166
I'm having a tough time getting rid of a ground loop hum in my home theater, and I'm looking for some tips.

My theater consists of:
- Denon AVR-2809 (2 prong power cable)
- Rotel RMB-1075 (2 prong power cable)
- Epson 1080UB projector (3 prong power cable)
- Sony blu-ray player (2 prong power cable)
- PS3 (3 prong power cable)
- Xbox 360 (2 prong power cable)
- Wii (2 prong power cable)
- Squeezebox (2 prong power cable)
- SVS Sub (3 prong power cable)
- Satellite receiver

With just that equipment everything was working great. No issues. Everything is run off the same circuit, but due to the location of the projector and sub, they are off a different outlet. I have moved them closer and tried off the same outlet, without success. Everything else is plugged into an APC Power Bar.

I added a Wyred 4 Sound DAC-2 in the hopes of improving my 2 channel experience, and now I've got a hum.

I'm using the HT bypass feature, so my front left and right go through the DAC, then to the Rotel. My surrounds and centre go direct from the Denon preouts to the Rotel.

I can make the hum disappear by disconnecting the HDMI cables for the projector, PS3 and satellite. If any of those are connected it will hum. I've completely removed the satellite from the equation (coax unplugged, HDMI unplugged, power unplugged) and it will still hum with the PS3 and/or projector, so it's not just ungrounded coax.

I can also make the hum disappear by disconnecting the interconnects for the surrounds and centre channels to the Rotel.

Lastly, if I use a cheater on the DAC power cable, the hum is gone.

Any advice on what to try? Since the cheater works, what would be a safe alternative, since I know cheaters are not to code, and am not interested in something that could be a potential risk.

I've tried grounding the Denon to the outlet, with no success. I'm really at a loss as to what to try.

Thanks,
Tyler
post #160 of 166
Will a soft hum (very faint...you need to put your ear close the sub to hear it) spoil a subwoofer in the long run?
post #161 of 166
Quote:
Originally Posted by Skylinestar View Post

Will a soft hum (very faint...you need to put your ear close the sub to hear it) spoil a subwoofer in the long run?

Of course not.
post #162 of 166
post #163 of 166
post #164 of 166
Hi all,

I admit I have not read this whole thread but I just wanted to share some pictures of the wire I installed that solved all my groundloop problems. It connects the groundplate of my coax wall socket to the ground of the of my electrical system to which ALL my AVR equipment is connected.

Maybe it's of any use as an example to any of you or if anyone likes to comment on my meticulous workmanship is that okay as well of course. :-)

Regards,





post #165 of 166
I believe you should only need to have your cable grounded outside where it connects to the house. That being said I have had the same problem solved in your fashion.
post #166 of 166
I don't understand electrical wiring so please bare with me. I have a buzz coming through the speakers in my home theater when the air conditioner auto switches it's mode. The AC is built into the wall and doesn't get it's power from a outlet. I replaced the receiver yesterday for anther reason, the buzz happens on both the old and new receiver.

What type of buzz is this most likely and would it be likely fixed by a power conditioner/filter or will I need an electrician?
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