I currently have the SuperFlower built EVGA SuperNova G2 750W powering my PC. Things were peachy until this scenario happened:

I was plugging in my Nvidia Shield's USB cable to my case's front USB 3 port. Something I have done many a time before. The Shield was not connected at the time. It was just the bare cable. My PC immediately shut off. Ever since then, I've been noticing a strange audio crackle/static that appears in certain programs and scenarios. I know it wasn't there before, and I'm not crazy. Certain games have it, while others do not. One guaranteed scenario I've found is ePSXe. I never had any audio problems of any sort before, and now it's a crackle/pop fest. This issue occurs on ALL my audio devices. Motherboard onboard, AND my external USB DAC (which is powered with its own A/C brick and therefore isolated)

Now, originally when it happened, I suspected the motherboard (MSI z97 Gaming 5). I had just gotten it, and it seemed like a mobo sort of issue to me. So I swapped it. I'm now running an Asus Maximus V7 Hero. Same issue. The rest of my hardware was pulled from my old computer (which had no problems like this) and is free of suspicion. I've tested without the graphics card, tested the memory, reformatted Windows, the works. It's been driving me mad. The ONLY thing that can't be ruled out is the PSU as it's also brand new. I'm starting to suspect that it has to be the culprit. Possible dirty power on the +5V line perhaps?

tl;dr - computer shut off and since then sound crackles and pops plague my computing experience yet everything else works flawlessly. Could it be the PSU? I feel like it has to be, but I know these are good units...