Question VRM Coil Whine

[budest]

Guys, I'm looking for some Devine Intervention to assist me here.

Built a new rig as follows:

Gigabyte Z390 Aorus Pro
32GB DDR4 3200
i7 9700K
Corsair iCUE H100i PRO XT RGB
Samsung EVO 1T SSD x 2
MSI Radeon RX 570 8GB ARMOR
Corsair CX750M
Corsair 275R Case
2 x 27" LG 4k Monitors

I use an external audio interface connected via USB to computer but DC powered.

Roland Duo Capture EX

It is connected to a set of monitors via XLR-6.3mm TRS Balanced cables

Behringer Truth B1031A x 2

I noticed electronic interference noise coming from my right monitor (which is positioned closest to my computer). Believing I also heard the same noise from inside my rig I opened the case up for a listen. Initially it was more of a cursory listen than full investigation.

Using a process of elimination I took the GPU out to rule out coil whine from it. That didn't solve the issue. I also had a PCI WiFi/Bluetooth card inserted and just to be sure to be sure I took it out too. Still the whine existed.
I then decided I would return the PSU, again to rule that out as the source. When I received the replacement the whine was still there. I narrowed it down to the CPU area and after doing some reading, discovered it was likely VRM whine. I contacted Gigabyte who informed me to disable the C States but that would only help if the noise occurred under stress. Given my rig hadn't been stressed yet I didn't hold out much hope but tried anyway. The noise was still there.

I also looked at ground loop issues. I firstly ensured everything was powered from the same power strip. That didn't help. I then tried connecting monitors to different power source, no luck. I tried connecting PSU to separate power supply from different room using an extension to rule a poor earthing in the room I was working. Still no luck.

I then ran another test. I have Pioneer DDR400 DJ mixer that is USB powered. When I connected the unit to the computer, (even without the external audio interface connected, so just the unit connected to computer via USB) there was awful interference noise through the monitors. At this stage the DDR400 was connected to the Behringers via twin RCA male to twin XLR male unbalanced cables. Appreciating the cables were unbalanced I then decided to try the same procedure with my MacBook. I connected the DDR to MacBook via USB and using the same unbalanced leads from the DDR 400 to the monitors there was no electrical interference noise at all. Silence. And they worked properly.

So I had ruled out the cables being the issue, the DDR400 causing any issues, the USB lead being the problem and the external audio box being the problem, as that was disconnected and isolated.

I then powered down the computer and then connected the DDR400 via USB to the computer to power it up only. There was an awful hum from the monitors. Then as I started the computer the hum turned to squelching and then to the horrible noise I refer to above once it have fully loaded.

The noise is definitely coming from inside the computer and contaminating the USB signal leaving the computer. Another thing I noticed was even with the external audio interface powered off using just the power button on its rear, but with the USB cable still connected to the computer, the noise from the monitors was ongoing. I would have to physically remove the USB cable from the interface to stop the whining. So I'm thinking at this stage that the noise from the VRM is leaving the rig via the USB, into whatever device the USB in connected to and being picked up by the monitors that are connected to that device.

I appreciate that is a lot of information and possibly not very well laid out. My overall point is that I'm coming to you having already tried a plethora of troubleshooting techniques over the period of a week. It seems that a lot of boards have VRM whine and those of sensitive hearing are prone to annoyance from it. My issues isn't so much the coil whine internally but that it's contaminating the external sounds sources.

I don't think it's a ground loop so don't believe a GL isolator would help. What am I missing or not doing? Can anyone see something I can't in what I have described? I have the MB stripped out ready to return but my fear is that, as many online are saying, their replacements have just been the same.

 

[budest]

Quick update:

I went back into the room and messed around a little with a clear head today. I have discovered that the single monitor that was transmitting the internal noise has a faulty power adaptor. I decided to swap the adaptors over just to rule it out and found that when the power lead from the 'good monitor' was put into the socket of the 'noisy monitor' the sound went away. I will experiment more with this later and update accordingly.

Having read dozens of posts on as many forums I haven't discovered anyone suggesting this as an issue so it's worth updating until full resolution for anyone else with similar problems.

 

[budest]

OK, just to update this thread for future reference, as promised.

The issue turned out to be easy to resolve but a complicated nightmare to find.

It wasn't a faulty power lead, as I thought. After changing my motherboard, twice, replacing all SATA cables, changing PSU's and removing almost everything connected to my board along with trying multiple audio interfaces and changing all my audio cabling, I discovered that the coil whine on the board was being caused when I connected my Roland Duo-Capture EX to the computer via USB. It began almost instantly the minute the USB lead was inserted and stopped instantly when it was taken out. It didn't matter what type of USB lead I used or what port I had it connected to or whether I connected it to an AC powered USB hub, the whine would still occur. Just as a reminder, the whine would then transfer out to my studio monitors and it was this that was driving me nuts. Even using different USB audio interfaces didn't change much.

Anyway, I read that if your audio interface doesn't need to be powered via the bus you can cut the black and red wires inside the cable and that prevents the interference I was hearing. It worked. It has something to do with all components carrying the signal being earthed thus enabling signal interference noise. Somewhere in the chain the earth needs to be broken (paraphrasing). So my cutting the earth in the USB lead that sorted the problem. Here's the thread:

https://www.gearslutz.com/board/geekslutz-forum/805656-dsi-mopho-x4-ground-loops-botched-usb.html

My (now educated) guess is that my problem is ultimately my Behringer monitors. I have read that they are prone to electromagnetic interference issues. It has to be them as I have changed everything else and the noise continued. I plan to replace them in the near future and will of course update this thread if replacing them did fix the issues properly.