I’ve found very little on the forum about this. For months I’ve noticed a type of whining noise in my IEMs and FOH. After extensive troubleshooting (trying different cables, balanced vs. unbalanced cables, different USB ports, with and without power conditioner, powered and unpowered USB hubs, unplugging CPU fan, etc.), the problem persists. I don’t have a GPU card, either, and those seem to be culprits sometimes. The only way I got rid of it was to use an entirely different computer - my backup machine which is a laptop - no noise).
I narrowed the noise down to the power supply in my main computer, which is a rack-mount PC. I’ve heard it called “coil whine”. To be clear, this is audible only through the audio coming out of the PC via the USB-C cable to my audio interface. I don’t notice any noise at all directly off the PC. I actually found an audio file someone posted who had the same exact noise as mine. Interference Example - Clyp (there was no solution given on the thread this came from)
Nothing seems to get rid of it. I brought this up to the Amazon seller and I eventually got an identical replacement (only option). Same noise. The PSU was not a very reputable brand, so perhaps an upgrade is in order.
(The example sounds like digital interference but not like traditional coil whine. Coil whine comes directly from the VRM’s in your system and it is audible without any audio equipment.)
About the problem:
Does it (also) occur when you use the system standalone: Not attached to foh or something else (not even your guitar/keyboard/mikes), so no extra cables attached to the system? It could be a ground loop.
Are you using an external audio interface or an inbuilt audio card? I would try using an external audio interface.
Btw: I have this kind of problem when my guitar comes really close to my computer, but that’s clear enough: the elements pick it up.
That’s what I can come up with. Typically, this kind of issues is hard to solve.
Edit:
“Coil whine comes directly from the VRM’s in your system” - as far as I understand.
The PC is in a rack by itself. At gigs, I have the digital mixer stacked with it, along with my power conditioner, but at home, the PC rack is by itself. The other racks aren’t even powered on. My home space is an entirely different setup and environment than a gig, yet the noise is still there at the same level. To answer your questions……..
Does it (also) occur when you use the system standalone: Not attached to foh or something else (not even your guitar/keyboard/mikes), so no extra cables attached to the system? It could be a ground loop. I have connected this minimal chain: PC > USB cable (different ones) > USB hub (different ones) > interface (bus powered) > mixer (nothing else plugged into mixer) (different mixers, too) > headphones. The only thing I can’t swap out is the interface so I swapped the PC for my laptop. Same chain otherwise. Zero noise.
Are you using an external audio interface or an inbuilt audio card? I would try using an external audio interface. External
It’s just odd that the noise doesn’t fluctuate in volume or pitch. Like that audio clip demonstrates, it’s constant. PC fans spinning up don’t affect it. Proximity to other gear doesn’t affect it. I’m at a loss.
The only times I’ve had a noise problem such as that was on my laptop when connected to it’s charger/power supply. If I let it run on battery there was no problem.
I finally tracked down this awful noise. I ground-lifted the power cable for the PC! I had previously ground-lifted the power cable for the power conditioner that the PC is always plugged into, thinking that anything plugged into the power conditioner would also be ground-lifted. Apparently, that’s not true, though I don’t completely understand it. Zero noise now, though I need to run the PC ungrounded.
