Help! Speaker/Sub Hum associated with Cable & HTPC
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Help! Speaker/Sub Hum associated with Cable & HTPC
I'm getting a lot of humming from my living room surround speaker system, most notably my subwoofer.
I have Sharp LCD TV & Onkyo AV Receiver with inputs from DVD player, CD player, Xbox360, HTPC and Cable box DVR. The problem seems to be associated with the DVR/Cable signal and/or the HTPC.
I can best trouble-shoot it with a DVD playing during a 'quiet scene'. I can then eliminate the hum by
1) disconnecting the Sub (faint hum from still present from other speakers)
2) disconnecting HDMI output to TV (obviously unacceptable)
3) disconnecting the cable from the wall
4) unplugging the HTPC (note, i tried putting it on a power strip but even in the off position, it still hums) or unplugging the audio output.
I have a feeling it is an electrical grounding issue... but I don't really know how to approach a fix.
My HTPC was recently upgraded from onboard digital Coax sound to a PCI sound card for surround. Since then, it seems to have gotten worse in that now I also get the hum when watching cable TV & DVDs. I've tried physically separating the cables the best I could, with no improvement. Also I've tried plugging the HTPC in with an outlet from another room, to no avail.
I've had the cable guy out twice, but they seemed to have no idea what could cause such a thing, and were unable to offer a fix.
There are a number of suggestions from various online forums, most seem to point to getting an in-line ground loop isolator; ~$50.
http://www.axiomaudio.com/groundisolator.html
I'm not thrilled about the cost, and I'm worried about potentially degrading the incoming signal? or it not fixing the problem!
I didn't see any discussions on this topic at spcr, and thought it would be good to get some input.
thx!
I have Sharp LCD TV & Onkyo AV Receiver with inputs from DVD player, CD player, Xbox360, HTPC and Cable box DVR. The problem seems to be associated with the DVR/Cable signal and/or the HTPC.
I can best trouble-shoot it with a DVD playing during a 'quiet scene'. I can then eliminate the hum by
1) disconnecting the Sub (faint hum from still present from other speakers)
2) disconnecting HDMI output to TV (obviously unacceptable)
3) disconnecting the cable from the wall
4) unplugging the HTPC (note, i tried putting it on a power strip but even in the off position, it still hums) or unplugging the audio output.
I have a feeling it is an electrical grounding issue... but I don't really know how to approach a fix.
My HTPC was recently upgraded from onboard digital Coax sound to a PCI sound card for surround. Since then, it seems to have gotten worse in that now I also get the hum when watching cable TV & DVDs. I've tried physically separating the cables the best I could, with no improvement. Also I've tried plugging the HTPC in with an outlet from another room, to no avail.
I've had the cable guy out twice, but they seemed to have no idea what could cause such a thing, and were unable to offer a fix.
There are a number of suggestions from various online forums, most seem to point to getting an in-line ground loop isolator; ~$50.
http://www.axiomaudio.com/groundisolator.html
I'm not thrilled about the cost, and I'm worried about potentially degrading the incoming signal? or it not fixing the problem!
I didn't see any discussions on this topic at spcr, and thought it would be good to get some input.
thx!
Sounds like ground loop to me. One thing you can get is a surge protector that has plugs for cable too, then route all cables to the audio setup through it.
The thing is, tv sets are usually grounded by the cable, amps not at all, and PCs from the power outlet, and the cable ground can be at a different potential than the power outlet ground. The surge protector will make the cable ground be equal to the power outlet ground.
The thing is, tv sets are usually grounded by the cable, amps not at all, and PCs from the power outlet, and the cable ground can be at a different potential than the power outlet ground. The surge protector will make the cable ground be equal to the power outlet ground.
Surge Protector vs. "Power Centers"
Do I just need any surge protector with coax pass, or should I get one of those fancy "power centers"? i.e. from Monster.
They claim to 'clean' the power and enhance video & audio. But there seem to be a lot of mixed reviews from consumers, and I haven't seen ANY professional reviews. These also can come at quite a cost, upwards of $300!!
Would SPCR consider weighing in on the benefits of 'conditioning' incoming AC power? I don't see anything in the forums currently!
http://www.monstercable.com/power/Monster_Power.asp
They claim to 'clean' the power and enhance video & audio. But there seem to be a lot of mixed reviews from consumers, and I haven't seen ANY professional reviews. These also can come at quite a cost, upwards of $300!!
Would SPCR consider weighing in on the benefits of 'conditioning' incoming AC power? I don't see anything in the forums currently!
http://www.monstercable.com/power/Monster_Power.asp
Last edited by bkoehn on Tue May 05, 2009 8:13 am, edited 1 time in total.
Those things are worthless for grounding issues, IME. Or vastly overpriced.
http://www.tripplite.com/en/products/mo ... delID=2814
This company makes the real deal, IMO, at least short of special per-outlet blocks.
http://www.tripplite.com/en/products/mo ... delID=2814
This company makes the real deal, IMO, at least short of special per-outlet blocks.
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bet all you need is a ground loop isolator on the sub input.
http://www.google.com/products/catalog? ... ps-sellers
http://www.google.com/products/catalog? ... ps-sellers
Eureka!
The in-line Coax surge protector worked GREAT!
Well worth the $20 investment.
Note, the hum wasn't isolated to the sub only (though most noticeable there), so I don't thing a "ground loop isolator on the sub input" would have worked.
cheers!
Well worth the $20 investment.
Note, the hum wasn't isolated to the sub only (though most noticeable there), so I don't thing a "ground loop isolator on the sub input" would have worked.
cheers!
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Glad to hear this worked for you. I had a similar issue when I first picked up a cheap sub amp for a custom subwoofer I was making. At the time, I was using a shuttle SFF PC. Only got the noise when the Coax SPDIF audio was connected to the stereo. I found that grounding the actual shuttle case helped. I've since killed that thing and my new Antec NSK1480 case doesn't appear to have this issue as it uses a standard PSU that is itself grounded as opposed to the Shuttle which had an external DC brick. But I do notice the TV signal gets a little fuzzy when the HTPC is on. So I think I'm still getting some grounding issues. I'll have to try this.