Ground Loop issue after rebuild

[drichardb]

Over the last few days I have been tearing my hair out trying to chase down a ground loop that has manifested.

My original build was (only listing components that should be relevant)
Aorus X570 Pro Motherboard
Inno 3D GTX 1080
Sound Blaster AE-9
TP-Link Wifi-AC internal card.
EKWB Watercooling loop with EK Fans.
2 xCorsair simple red LED Fans
Corsair AX760i PSU
Phanteks Enthoo Pro Case.
Corsair K70 Keyboard
Logitech G502 Mouse

Sound System
Pioneer SC-LX72 AV Receiver
B&W Front and Center Speakers
Logitech satellites
REL T7/x Subwoofer

Everything was awesome. No issues at all.

Last week I bought a Lian Li O11D Evo Case a Seasonic GX-1000 PSU, some new corsair RGB fans.

Rebuild went smoothly however I now appear to have a ground loop in the system which is slightly noticeable on desktop when moving the mouse but becomes very loud when launching into a game to the point where you have to turn the sound up to drown it out.

So far I have tried, in order and all without success
Switched to a GTX780 GPU
Unplugged the Display Port cable
Switched back to the Corsair PSU
Removed the Sound Card
Removed the wifi card
Disconnected the Corsair RGB controller
Disconnected ALL the case cables (USB/Sound/RGB) except the switch connector
Disconnected all bar one logitech speaker from the Amp

As it stands my system consists of
Lian Li Case
Aorus Mobo
GTX1080
EKWB Watercooling Loop with two Corsair Fans (RGB not plugged in)
Corsair PSU

Rebuilding back in the Phanteks case is no longer possible as it was donated to another family member who was visiting at the start of the easter break - hindsight is a wonderful thing, never expected to encounter this!

So in my mind I've reduced the system down to a known good config, with the exception of the fans which I'm reluctant to unplug (along with the pump) in case of damage to the CPU but in researching this issue I've yet to find anything relating to fans being culprit.

In short - what the <long string of expletives> could possible be causing the ground loop and how can I eliminate it?

Any advice or suggestions for other steps I can take would be massively appreciated.

 

[drichardb]

I've no idea what's causing the noise issue, however I'm going to tell you something relating to grounding.

Cases are painted and this paint stops them being earthed correctly.

In this first picture I've sanded the PSU screw areas on my Silverstone FT-02 case, I've also not used the Seasonic painted screws and used regular silver screws.

I have also added HDD grounding scraps to my HDD's that are held in plastic anti-vibration, see second photo.

Again no idea if these ideas will help but gives some ideas that could help.

Thanks for replying Jason,

I've currently got the PSU outside the case sat on a cardboard box so I think it would be fair to discount that?
As for Hard drives, I've got an m2 ssd plugged into one of the motherboard sockets and nothing else so no dice there either...

 

[drichardb]

The PSU should be installed to the case as the 4 screws that hold the PSU are the only case grounding. Having the PSU outside the case means no grounding.

You should also sand the paint from the PSU screw locations and use standard silver screws (not painted) to make the best grounding connection.

Fair enough - I routed the cables round the back, mounted the psu and used some plain screws with serated surface to grind the paint off down to bare metal (no sandpaper here at the mo).

For as long as pump is circulating coolant it's OK to have fans stopped temporarily.

Thanks for the reassurance - Disconnected the rad fans at the same time as remounting the psu.

Neither have sorted the issue

Are you sure it's really a ground loop (a hum at mainly 50Hz mains frequency)? It seems odd that a ground loop would come and go with mouse movement and disk/CPU activity. I once had a motherboard though where the on-board audio was susceptible to EMI, and mouse movements caused a buzzy/chirpy noise.

A few thoughts/questions that might help you get to the bottom of it:
Assuming the noise is via the AV amp and speakers, does it stop if you change input to something other than PC?
Are you using the AE-9 for headphones - do you hear the noise on them too?
Have you changed the way the audio is fed to the AV amp? E.g. optical before and analogue now, or AE-9 before and motherboard now? Have you tried optical?
Have you changed how the PC and AV amp are plugged in to the mains?

Good luck!

99% certain it's ground loop - not noticing any sound with disk activity (it's an nvme device plugged into the mobo after all), its faint but noticeable when moving the mouse and is at its loudest when the GPU kicks into gear once you get beyond the initial loading screens and rendered objects start appearing on screen. I have tested with two GPU's (GTX 780 & 1080), both produce the same.

This clip on youtube is pretty much identical to my issue - https://youtu.be/LtUB367g4Vo

To answer your questions - does it stop on input change? Yes
Am I using the AE-9 for headphones? No but when I had the front panel audio connected to mobo it did stop with a pair of Sennheiser HD569's plugged in. I have also tried plugging in my Harmon Kardon Go+Play speaker via 3.5mm cable while it was connected to its mains charger, no sign of the noise on there.
Have I changed the way the audio was being fed? QED RCA Interconnects for the fronts and 3.5mm to twin RCA for the other channels before and after. Not tried Optical as I want the EQ control that is only available through analogue. MIght dig out the optical cable that came with the card to test that in a bit.
Any change to mains setup? No, same cables same extension plug, same socket. Before my dinner I popped down to local trade store and got a socket tester, checked every socket on the extension and the mains and all read correct for wiring.

***edit***
optical cable located and tested with both on board and AE-9 audio - no noise detectable. but the sound quality is pants compared to the analogue AE-9 connection so the quest continues...

 

[drichardb]

Just transplanted the system. Didnt feel the need to reinstall at this point.

 

[drichardb]

I can see you have a wifi card and does your motherboard also have bluetooth?

If so, turn all wifi and bluetooth off completely on your PC and see if you still get the same.

Thanks for the suggestion, mobo only has wired networking and no BT capabilities. Wifi card (which does have BT) was removed from case during troubleshooting (see OP ) with no change in symptoms

 

[drichardb]

Hmmm, puzzling (sorry, couldn't resist). When you say that you connected your HK battery(?) speaker, was that to the AE-9 analogue outputs or the onboard outputs? It would be good to narrow it down to being a problem with onboard and/or AE-9 analogue outputs, and whether the noise is present with / without your AV amp.

I just looked at the soundblaster AE-9 specs and it says you need to connect PCIe power if using the external ACM thingy. Any chance that's the problem?

Thanks for the reply wonko -
Tried it with both onboard and AE-9, no noise from the HK when connected to either source. Tried it on the center and surround channels too for good measure, still no noise from the HK.

I don't use the ACM module but I have got the card plugged into a dedicated 6 pin power cable. will disconnect it and see if it can run on socket power only.

JasonM...

"Is the sound card installed back in same slot it originally was?" Yes and i've tried it in the adjacent slot too

"If the card has PCIe power, is there anything sharing that cable, or does it have it's own dedicated cable going back to the PSU?" dedicated cable from the modular PSU

"Is the dongle for your wireless mouse connected back into the same previous USB port?" Its the wired version and is plugged into the original socket

"Is the sound card earthed to the case, or again is the case painted around the cards metal bracket? (meaning sound card could not be grounded)." Will have to check that (just got back from first round of golf in almost 2 years!)

"Have you checked the RCA connections connecting sound card to amp are clean? Do you have any electronic cleaner to clean the contracts? Poor contact on outer shielding can cause hum / interference?" I'll check them but I don't anticipate an issue, they are QED brand cables less than 6 months old, bought at same time as the AE-9.

"Have you tried a different RCA cable?" Yes

"How is your computer plugged into mains, are you using the same mains plug / setup as before? Have you changed anything like plugging the amp into a shared extension next to PC IEC?" No change at all to the mains setup (all devices into one "gang" plug, same socket config as before)

"If you run a graphics card load test, does the sound interference get worse?" Will get back to you on that after dinner

"Have you checked you have not accidently put the computer source volume low, forcing you to put amplifier gain up, highlighting interference that was always there but you never noticed before?" Definately no issues there

"Have you moved your amplifier, or moved any PC cables close to it, that were not near it before." Everything exactly as it was - simply unplugged from the Phanteks build, plugged into the Lian Li

 

[drichardb]

Thank god for working from home....logged off and ran to the utility room to grab an extension reel as the nearest socket is on the other side of the room.

With amp cranked to max the noise is there but you have to put your ear about 6 inches from the speakers to pick it up. At "normal" volume, sitting at the desk you wouldnt notice it.

I'm not gonna call fixed just yet as I now need to complete the build again with new PSU/fans etc. Was planning to see The Northman in cinema tonight but that might have to wait for another day following this revelation! Watch this space...

 

[drichardb]

Got distracted by the football so took a bit longer than expected...

Rebuild just about complete. Just waiting on a splitter to give me a few more USB headers to control the fan lighting but otherwise everything is in and powered up.

Switching to the new PSU kicked the noise up a bit so I've upped the gain on the AE-9 a few db's so I can run the amp about 10% lower, I might bump it up further so long as it doesnt affect the sound quality. Fortunately you can't hear it on desktop but for now its at the point where I can live with it.

Busy for the next few evenings so hopefully I'll have a clear day on Sunday to open it back up and improve the cable management, especially the fan cables (6 RGB fans creates a LOT of mess). Longer term I'll be revamping my room at some point in the next few months, desk isnt big enough to handle the 42" OLED I've got my heart set on. That will require my amp to move closer to the other socket along with new extension cables and a few other tweaks too. With any luck that will further improve the situation but for now I guess we can call this done.

thanks again to everyone for your suggestions

 

[drichardb]

@JasonM
I was typing up my last post and didnt realise you had also replied. Are you able to send me any links to the power cords you use please?

This has been a completely alien situation for me, if they are reasonably priced, or I can find something equivalent at a more palatable price I'll definately consider it.

I used to have an ASUS Xonar D2X until a few years ago, was gutted to get rid of it but the volume started to fluctuate a lot. Easily one of the best sound cards ever made though this AE-9 has really impressed me in the few months I've had it.

 

[drichardb]

I know what you mean about the snake oil claims, I've seen enough of it with interconnects and speaker cables. The limited testing I've been able to do in that area has told me that good quality can be had for modest amounts so I generally draw the line at £40 to £50 any more than that and the diminishing returns are too much for my wallet to handle - I don't have deep enough pockets to indulge myself more than that unless I get promoted at work! I'll definately keep an eye on ebay though and hopefully pick up a bargain or two

 

[drichardb]

Agree 100%. I snagged a 3 meter set of QED Performance 40i RCA interconnects from my local branch of Audio T when I was buying my subwoofer last year. Paid £40 rather than the £90ish sticker price. Bit longer than I need right now but already had in mind the furniture revamp I mentioned earlier. It was a case of "I'm gonna need them soon, I'm buying an expensive sub, make me an offer I can't refuse", and they did!

 

[drichardb]

By happy coincidence I bought a 3 meter version of that for my sub, think I got at least a tenner off it too

I do get where your comming from about the crazy price you can pay for audio kit in general, not just cables. Last night I watched a youtube vid where this guy up in London had spent north of 250k on his hifi. The CD player alone was split into about 4 components. Absolutely bonkers if you ask me but if I was a multi millionaire then chances are I would drop a very large chunk on hifi but not that kind of silly money.

The overall argument, at least to me, is more about peace of mind than anything else. Better to spend a small amount and be satisfied with your setup than have that doubt in your mind which spoils the enjoyment. I can honestly say these last few months (post subwoofer/soundcard/cable upgrade) have been the most enjoyable Ive had in many years so on that basis alone I consider my investment so far to be money well spent