Speaker hum after connecting AVR to HTPC - AVS Forum
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post #1 of 9 Old 10-08-2013, 06:08 AM - Thread Starter
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I have an Onkyo HT-3400 and I've been using it with PS3, a set top box and a small HD media player with no issues. Since I've got my HTPC and connected it to my AVR via HDMI, I can hear a faint buzz in the speakers, more prominently from the Sub. I cannot hear the hum when the HTPC is off and I'm using any of the other devices.

Did anyone of you experience this before? Any solutions for me?
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post #2 of 9 Old 10-08-2013, 07:41 AM
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Seems like you have what's called "ground loop". Your home's electrical plugs might have a ground wire issue. How old is your home? Does it use 2 wire electrical or 3 wire (with ground). Some solutions are to plug all your devices to one common power strip so the grounds all match. If that doesn't help then try other combinations of plugs until the hum goes away.

It could also be coming from a coax line that isn't grounded to your house wiring properly. You might need to have your cable/satellite company come out and ground it. Experiment by disconnecting coax lines from your AV equipment one at a time until the hum goes away.

There's lots of info about this topic:
Search Results for Ground Loop
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post #3 of 9 Old 10-08-2013, 07:58 AM - Thread Starter
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Quote:
Originally Posted by hammerdwn View Post

Seems like you have what's called "ground loop". Your home's electrical plugs might have a ground wire issue. How old is your home? Does it use 2 wire electrical or 3 wire (with ground). Some solutions are to plug all your devices to one common power strip so the grounds all match. If that doesn't help then try other combinations of plugs until the hum goes away.

It could also be coming from a coax line that isn't grounded to your house wiring properly. You might need to have your cable/satellite company come out and ground it. Experiment by disconnecting coax lines from your AV equipment one at a time until the hum goes away.

There's lots of info about this topic:
Search Results for Ground Loop

I had already gone through a lot of topics and they seem to give the same suggestion as you did. I'm just wondering why the issue is just with the HTPC because when it is turned off or when the HDMI from the HTPC is removed or I switch to other sources on the AVR, the hum is gone. I have a Corsair CX500V2 power supply and an APC branded UPS both of which are supposed to give "clean" power to the PC. Also, I didn't expect a digital interface such as an HDMI to induce noise.

A few points to note is that I had a similar issue with my 2.1 Sony speakers with analog connections and I got rid of most of the hum by getting a better branded aux cable but it's still there. However, I don't hear this on any other audio device such as the TV or my AVR with all other sources except for the HTPC.
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post #4 of 9 Old 10-08-2013, 08:36 AM
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Is there a coax line going into any of your equip?
Is there a coax line going into the HTPC?
Is your cable/sat coax grounded at your home's fuse panel?
Is your "clean power" on the same wall outlet as your AVR, Tv, etc?
Can you plug everything- HTPC, AVR, Tv, etc into that clean power device?
Does the clean power device have coax in/out?
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post #5 of 9 Old 10-08-2013, 09:34 AM
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Quote:
Originally Posted by komalthecoolk View Post

I had already gone through a lot of topics and they seem to give the same suggestion as you did. I'm just wondering why the issue is just with the HTPC because when it is turned off or when the HDMI from the HTPC is removed or I switch to other sources on the AVR, the hum is gone. I have a Corsair CX500V2 power supply and an APC branded UPS both of which are supposed to give "clean" power to the PC. Also, I didn't expect a digital interface such as an HDMI to induce noise.

A few points to note is that I had a similar issue with my 2.1 Sony speakers with analog connections and I got rid of most of the hum by getting a better branded aux cable but it's still there. However, I don't hear this on any other audio device such as the TV or my AVR with all other sources except for the HTPC.

If you believe HTPC grounding is an issue, connect HTPC to the AVR using a non-conductive connection, such as optical.

If the noise is still present, then you know it is being generated by the PC.

I had to install a separate power line for the Living room set up because I could not isolate the noise.

6 TV's in the house on FiOS and we only pay $4.99/month to connect them all!!! Power to the CableCard and WMC7!!!
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post #6 of 9 Old 10-08-2013, 09:45 AM - Thread Starter
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Is there a coax line going into any of your equip?
The only coax is to the setup box connected to the AVR via HDMI. No hint of any noise/hum whatsoever.

Is there a coax line going into the HTPC?
No

Is your cable/sat coax grounded at your home's fuse panel?
Since I never noticed any kind of noise/hum/interference, I'm assuming it is properly grounded.

Is your "clean power" on the same wall outlet as your AVR, Tv, etc?
Yes but there an APC UPS between the wall outlet and the HTPC.

Can you plug everything- HTPC, AVR, Tv, etc into that clean power device?
I'm not sure it'll be able to handle the load when there is a power outage but for the sake of testing, I will try that out once.

Does the clean power device have coax in/out?
No
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post #7 of 9 Old 10-08-2013, 09:46 AM - Thread Starter
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Quote:
Originally Posted by blueiedgod View Post

If you believe HTPC grounding is an issue, connect HTPC to the AVR using a non-conductive connection, such as optical.

If the noise is still present, then you know it is being generated by the PC.

I had to install a separate power line for the Living room set up because I could not isolate the noise.

That makes sense., I can try that after getting the whole new set of connections required for this setup..
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post #8 of 9 Old 10-08-2013, 10:26 AM
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Quote:
Originally Posted by komalthecoolk View Post

The only coax is to the setup box connected to the AVR via HDMI. No hint of any noise/hum whatsoever.

Sometimes it doesn't matter. Disconnect that coax. Put the AVR on HTPC. Is there hum?


Also, is the hum coming through all speakers or just a subwoofer? Is the subwoofer power plugged into the same outlet as the AVR, HTPC, set top box?
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post #9 of 9 Old 10-08-2013, 01:44 PM
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I had a subwoofer hum that was only heard when the AVR was turned off. It was not heard when the AVR was on with the volume turned all the way down. Turned out to be the cheap coax going to the sub. The coax was picking up hum from the sub's power cord. And the sub would not turn off because the hum signal kept it on. It's as if when the AVR was turned on the coax was grounded better. I found out it was the coax by moving it around & the hum would change. So I bought a better sub coax.

You might try moving around some coax and/or power cords & see if your hum decreases or increases.
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