Finally! I think I've discovered the cause of pc-sub interference

JonnyTester

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For a long time now, I've battled with a low "rumbling" interference noise from my sub when my pc is connected to my receiver (by hdmi). I have gone as far as to connect a ground lead from my receiver chassis to a wall socket, with no success. In the end I just gave up, split my HTPC and sold off the components. Then at the weekend I connected up my everyday pc to my tv to check out a bluray disc I'd made of my daughter's wedding. I had forgotten all about the rumbling up to that point. Then when it kicked-in again, it doubled my resolve to find the cause. And I think I just have.

After ruling out multiple hdmi cables, I started to think about ethernet. I have a Virgin Media Superhub 3 running in modem mode, connected to a Linksys router. This in turn connects to a HP 8-port switch. All my ethernet cables are of the standard un-shielded type. I had never bought shielded cables, thinking it was just a money-making ruse. But just for curiosity's sake, I reached down and unplugged the ethernet cable from my pc. The rumbling stopped immediately. I tried a few of the everyday things I do on my pc, like running Word, Photoshop and a couple of other apps. The rumbling would always be there, but would stop for a while if the pc wasn't being used for any length of time. But when I would open an app, the rumbling would go nonstop. I have often linked it to hard drive activity, as it would correspond with the hdd led blinking on my pc case. Now there was nothing. And when I reconnected the ethernet cable, the rumbling was still absent. EUREKA!

Now I'm not going to kid myself that I have discovered a total fix. I'm not going to buy a dozen shielded ethernet cables of varying lengths. I don't even know for certain if shielded cables are the answer. But I am going to start with buying a couple of ferrite clamps for my pc and receiver power cables, just to see if they make a difference. But right now, I'm beginning to think I see an end to this infuriating issue.
 
For a long time now, I've battled with a low "rumbling" interference noise from my sub when my pc is connected to my receiver (by hdmi). I have gone as far as to connect a ground lead from my receiver chassis to a wall socket, with no success. In the end I just gave up, split my HTPC and sold off the components. Then at the weekend I connected up my everyday pc to my tv to check out a bluray disc I'd made of my daughter's wedding. I had forgotten all about the rumbling up to that point. Then when it kicked-in again, it doubled my resolve to find the cause. And I think I just have.

After ruling out multiple hdmi cables, I started to think about ethernet. I have a Virgin Media Superhub 3 running in modem mode, connected to a Linksys router. This in turn connects to a HP 8-port switch. All my ethernet cables are of the standard un-shielded type. I had never bought shielded cables, thinking it was just a money-making ruse. But just for curiosity's sake, I reached down and unplugged the ethernet cable from my pc. The rumbling stopped immediately. I tried a few of the everyday things I do on my pc, like running Word, Photoshop and a couple of other apps. The rumbling would always be there, but would stop for a while if the pc wasn't being used for any length of time. But when I would open an app, the rumbling would go nonstop. I have often linked it to hard drive activity, as it would correspond with the hdd led blinking on my pc case. Now there was nothing. And when I reconnected the ethernet cable, the rumbling was still absent. EUREKA!

Now I'm not going to kid myself that I have discovered a total fix. I'm not going to buy a dozen shielded ethernet cables of varying lengths. I don't even know for certain if shielded cables are the answer. But I am going to start with buying a couple of ferrite clamps for my pc and receiver power cables, just to see if they make a difference. But right now, I'm beginning to think I see an end to this infuriating issue.
How did you get on? i have similar issue just now.
 
How did you get on? i have similar issue just now.

Unfortunately the issue returned again. I have resigned myself to it being a permanent issue. The only other thing I can think of is that it is an earthing issue with our main supply. But whether its worth pa to get it investigated is another matter.
 
Unfortunately the issue returned again. I have resigned myself to it being a permanent issue. The only other thing I can think of is that it is an earthing issue with our main supply. But whether its worth pa to get it investigated is another matter.
I have really expensive top of the range kit in my system, Denon x8500 and Monitor Audio 5g Gold full AV package, 82" qled and a very expensive gaming rig pc i built myself. I recently bought a new Monitor audio Gold subwoofer to replace my existing Monitor Audio Silver subwoofer(which i had no isses with) upon moving to the gold subwoofer i started getting the low rumbling interference noise and it traced back to being the my pc. Now i tried everything, different cables, different wall sockets on diferent power line loop, different AVR, unplugged all internet devices, even took my pc and sub to a friends house. I could not find a solution, it seems to be my new sub does not like my pc and is picking up some kind of frequency from the pc. I am going to ask store if i can get a replacement subwoofer just incase its the subwoofer. I use my pc everyday so i need that more than the subwoofer not to mention my old subwoofer had no such noise.
 
I had a similar issue. I was using a very compact case with a 2070 super in it. My 1080ti made no noise but the 2070 super caused a rumble through the subs. I ended up moving the PC into a much larger server style case in another room and running a really long HDMI cable to the AVR. I also now have USB over ethernet into the cinema room which connects the PC to the minidsp and my subs make no noise.

This is what changed:

Different case, different motherboard (same GPU)
15m HDMI instead of a 2m HDMI (connected to the same AVR)
15m USB over ethernet but connected to the same devices at each end (minidsp, wireless keyboard dongle)

Do you have any USB devices connecting the AVR/subs and PC?
How does the PC connect to the AVR, just HDMI?
 
I had a similar issue. I was using a very compact case with a 2070 super in it. My 1080ti made no noise but the 2070 super caused a rumble through the subs. I ended up moving the PC into a much larger server style case in another room and running a really long HDMI cable to the AVR. I also now have USB over ethernet into the cinema room which connects the PC to the minidsp and my subs make no noise.

This is what changed:

Different case, different motherboard (same GPU)
15m HDMI instead of a 2m HDMI (connected to the same AVR)
15m USB over ethernet but connected to the same devices at each end (minidsp, wireless keyboard dongle)

Do you have any USB devices connecting the AVR/subs and PC?
How does the PC connect to the AVR, just HDMI?
Hi, thanks for your response.

So my pc is link to my avr through a high speed hdmi monster 6mtr cable, i tried a 2mtr one aswell.

Pc only has a usb bluetooth dongle and 2 x usb dongles for wireless mouse and keyboard.

Using a 2080 super connected to avr via hdmi.

Sub is atleast 12ft away from pc and sub is only connected to avr through a QED subwoofer cable going from sub LFE IN to avr subwoofer connection.

I could not get the noise to go away.
 
Does the noise disappear when you disconnect the HDMI cable?
 
In my case, I was having the problem with 2 pc's. I retired one of them and now just have one in a mid tower.

I have a modular psu, ROG Maximus Gene VIII m-atx motherboard, gtx 1060 super gpu, combo wifi/bluetooth card. I was using a 3m gold plated hdmi 2.0 cable from the pc to my receiver and have tried lots of different hdmi's with no change in the rumbling.

I have tried powering all my equipment from the same socket, powering the pc from a socket on a different phase from the rest of the equipment, powering the sub from a different phase, removing all the peripherals from the pc, using high/low quality long/short phono cables from the receiver to the sub, none of which made any difference.

But I have discovered that touching the hdmi cable to any metal part of the backplane triggers the rumbling. So the hdmi cable doesn't even have to be connected to trigger the rumbling.

I've resigned myself to never sorting the problem. Which is a pity because I have a pretty decent multimedia pc which will never achieve its full potential.
 
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I connected a bluetooth transmitter to the sub outs on my receiver, and a bluetooth receiver on the sub, and the noise is there even when connected wirelessly. This would suggest the receiver is outputting the signal on the sub channels, removing the sub from the list of culprits.
 

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