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Audio interference.

IanDav

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Hello all.


I have a sound interference issue, which is driving me mad. Let me elaborate.

I won’t go into detailed PC specs as I’m not sure that’d be necessary, but this is it in brief:


i5 10600k

MSI Z490 Gaming Edge MB.

RTX 3080

EVGA 750W SuperNOVA G2 PSU.


I recently bought a new VRR TV (Samsung 75” Q95T, which is brilliant by the way) for the living room, so I decided to run some cables to it, from my bedroom above, where my PC lives. I ran 5 meter lengths each of HDMI (into the One Connect box), optical (into my Rotel processor) and a USB cable, which connects and extends via a powered hub in the living room, to which I have a keyboard, mouse, two game controllers and sometimes headphones connected. I quickly discovered that I have some awful interference when gaming, and also at other times, even when component stress is very low. I use Launchbox, for example, which is front end software primarily for use with emulation. It’s certainly not remotely stressful for a system like this, but I get variable buzzing and interference when scrolling through games on that. If I load up World of Warcraft, then turn the game audio down in the interface and just move the camera around, it sounds awful, again with variable noises etc coming through my speakers.


I usually have this PC connected to a Denon surround amp in the bedroom, also via a shorter optical cable which I just unplug and change for the newer longer cable, and I have no sound issues at all with that. That being the case, I initially laid the blame on one of the cables with them being the new addition. To test the cables further, I connected all three of them to a PS4 Pro, only to find that all three cables work flawlessly, with no sound issues whatsoever. So that 99% rules a bad cable out I concluded.


Sound duties on my PC were being carried out by the onboard audio, so to eliminate that from the equation, I bought a Sound BlasterX AE-5 (disabling the onboard audio it goes without saying), hoping that would save the day, especially with it being so well reviewed too. However, no, it was just the same. I then tried an external DAC (Sound Blaster X3) but again, no difference.


Another thing is that if I use my headphones on the hub in the living room to pick up the sound through USB, the sound is perfect.


At first I was wondering if it was the video card, as I’ve read about people having issues with Nvidia GPUs causing sound interference, but then, surely I’d hear that when the sound is sent to my Denon amp. Or if it’s some kind of power issue. I’m aware of ground loop problems (which I know little about) but any forums I’ve read don’t quite hit the mark with exactly what I’m experiencing, with a lot of examples not quite being the same as mine.


Has anyone had this same issue or something similar?


Any advice would be great.


EDIT: After typing this out, I have since tried unplugging the HDMI cable, which I should’ve done sooner. I can confirm that the sound problems stop when this is not connected. So, would that make it a grounding issue with the components not being plugged into the same outlet? I’m in the UK, by the way, if that makes a difference.
 

RayDunzl

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So, would that make it a grounding issue with the components not being plugged into the same outlet?

Easiest place to start would be to use the same outlet, no?

I use one wall outlet with many added outlets here, with no audible noises, and its a real rats nest of wires and cables, not that I'm proud of that, but there's no problem to fix.
 

somebodyelse

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Easiest place to start would be to use the same outlet, no?
With a 5m extension lead running between rooms on different floors so that everything related in the other room can be powered from it? It sounds like the start of an electrician's horror story - not strictly wrong per se, but the first link in an unfortunate chain.
EDIT: After typing this out, I have since tried unplugging the HDMI cable, which I should’ve done sooner. I can confirm that the sound problems stop when this is not connected. So, would that make it a grounding issue with the components not being plugged into the same outlet? I’m in the UK, by the way, if that makes a difference.
It does seem like a grounding issue. Being in the UK I'd guess your upstairs and downstairs sockets are on different rings too (separate breakers at the consumer unit) which won't help. An optical HDMI extender would isolate it. I gather the HDMI-over-CAT6 extenders usually do too, but I've not tried either.
 

tonycollinet

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This will be a ground loop probably between your PC, TV and whatever amps are in place. It is not totally clear what is the source for the audio (I think your PC), and how that is connected to the other components which makes it very difficult to suggest what to improve.

However the most likely solution would be to electrically isolate your source from somewhere in the chain - and the best way to do this is to use an optical toslink connection.

So for example if you have USB from the PC carriying audio - if you convert that to Toslink - or just use a toslink output from your pc instead of USB, that may well improve the situation.

But only if the ground loop is not perpetuated by one of the other cables - eg if the HDMI is connected to the TV and the TV is also connected to the amp.
 

AnalogSteph

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Sounds like a ground loop indeed. Unfortunately the most interesting connection - namely what the soundcard audio out is plugged into - was left out, but I assume it goes into an unbalanced input of something that is grounded via wherever. A standard problem when connecting a PC to a home cinema system with unbalanced audio cabling.

I would investigate whether getting the audio across via HDMI / HDMI ARC is an option.

If the connection from PC to HT system already is Toslink, then it gets interesting. In that case I have to suspect that the (obviously unbalanced) connection from Rotel processor to power amp(s) is part of a ground loop somehow, which in turn may have been completed by the HDMI cables from the PC. It may have been there before, remaining unnoticed before the PC with its more problematic mains currents entered the picture.
 
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IanDav

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Okay. Thanks to everyone for the input, for a start.

Work has dictated that I’ve not been able to give this much attention since my post, but today I ran an extension cable from the living room, where my processor and power amplifier etc are plugged in, up to the bedroom, so I could power the PC from the same outlet.

Hey Presto, no interference at all. So, I suppose that tells us that it is a grounding issue after all. That was an easy thing to check in the end, but this issue was new to me even though I now know it’s a common problem.

With that in mind, are there any good devices / fixes that folk use before I start getting a spark involved?
 
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tonycollinet

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Yes - optically isolate the PC from your processor/amplifer using toslink. You could use a simple usb to toslink box as an intial test to see if it solves the problem.
 
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IanDav

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Yes - optically isolate the PC from your processor/amplifer using toslink. You could use a simple usb to toslink box as an intial test to see if it solves the problem.
Could you expand on that please, as I'm not sure what you mean? The PC is already connected to the processor via optical / toslink directly from the rear I/O.
 

tonycollinet

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Ah - then you already have your audio connection isolated, and my proposal is useless to you. So the ground loop must be caused through one of the other connections. USB to keyboard / mouse, or the hdmi.

It is difficult to predict what might be going on without some sort of interconnection diagram. Are there additional connections between the HDMI Box or Hub to either the processor or amp? (even if via some other device, like the TV. If there are, try disconnecting them.

You could also try disconnecting the HDMI and USB in turn (and then both) to see if one or both of them are part of the ground problem.
 
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IanDav

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I disconnected the HDMI cable last week just after I posted my query, and all interference stopped, so yeah, it seems tied to that somehow. I thought the HDMI cable was faulty at first, but when I connect it to my PS4 Pro (along with the optical and USB I am also using on the PC for connection downstairs) and send that down to my living room, everything is fine.
 

tonycollinet

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Is the HDMI switch box also powered? (I assume that is what it is). If so, try plugging directly into the destination.

Also try unplugging any other devices from the box.
 
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IanDav

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It isn't a switch box as such. It goes from the PC directly into the One Connect box on the TV (Samsung Q95T), so there's nothing in between the source and the display. I'll try unplugging some other stuff tomorrow, although, I almost don't want that to work as that'd just cause me more of a headache!!
 
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IanDav

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Just in case you've not seen that particular model.
 

tonycollinet

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It isn't a switch box as such. It goes from the PC directly into the One Connect box on the TV (Samsung Q95T), so there's nothing in between the source and the display. I'll try unplugging some other stuff tomorrow, although, I almost don't want that to work as that'd just cause me more of a headache!!
It gives you information - which you use to solve the problem. EG if you have electrical connection from TV to processor or amp, and removing that eliminates noise, then if you can replace that connection with optical you'll solve the issue.
 

somebodyelse

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Jensen Transformers' application notes have fairly comprehensive coverage of grounding issues and how to solve them, although they don't talk about HDMI directly. AN006 is a potted summary while AN007 has full detail. They're US-centric on some aspects of the mains supply, but the same rules generally apply. I mention this so that you can find a solution that's future proof rather than one that works for now but has the problem return when you upgrade or move something.

Having a house where one of the upstairs sockets is a spur from downstairs, and a few were originally storage heater outlets, I can tell you having an 'odd' socket is a recipe for future confusion. I'd keep that as a last resort, and start looking for isolating HDMI extenders as mentioned before.
 
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IanDav

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It gives you information - which you use to solve the problem. EG if you have electrical connection from TV to processor or amp, and removing that eliminates noise, then if you can replace that connection with optical you'll solve the issue.
I didn’t want what I said to make it sound like I couldn’t be bothered, and of course you’re correct. I’ll have a look into that once I get this week out of the way.

It’s just a little frustrating as it was something I did on a whim, thinking ‘that would be nice, if I could run my emulators etc on the new TV’. I was excited to show my dad some of the old games from the Spectrum and Amiga days that we used to play, only to find that when they came to our house, I couldn’t because of the garbage sound.

Enough of that…

I’ll disconnect some other things from the TV, and see if they make a difference. Of the top of my head, I think it’s just my Blu Ray player and a Firestick.
 
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IanDav

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Jensen Transformers' application notes have fairly comprehensive coverage of grounding issues and how to solve them, although they don't talk about HDMI directly. AN006 is a potted summary while AN007 has full detail. They're US-centric on some aspects of the mains supply, but the same rules generally apply. I mention this so that you can find a solution that's future proof rather than one that works for now but has the problem return when you upgrade or move something.

Having a house where one of the upstairs sockets is a spur from downstairs, and a few were originally storage heater outlets, I can tell you having an 'odd' socket is a recipe for future confusion. I'd keep that as a last resort, and start looking for isolating HDMI extenders as mentioned before.
They look really interesting. Thanks for that. I’ll certainly have a read through them.

I considered running the extension from where the home cinema equipment is powered up through the ceiling, but the only route that could take without starting drilling holes everywhere would be by the side of the three cables I already mentioned, which could introduce more problems, so that’s a no go really.
 
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