No sound from B450 Pro4 Realtek Audio driver

I had the same problem with a B550M Pro 4 motherboard in Win10.

Sound suddenly stopped working from both the front and rear ports. Instead there was just loud static. Inside Windows there was no error and sound card was still available in device manager. Using different speakers / headphones didn't fix the problem. Sound output device in Windows was verified and was correct.

Drivers were up to date. ASRock suggested re-installing them, but that didn't help.

In the end it was a hardware fault. I replaced the motherboard with an identical model motherboard (using the same boot drive, drivers, headphones and same everything else. No software was changed or re-installed).

Problem was fixed. So it was definitely a bad MB in my case.

Given that there are a number of other people complaining about the same issue in various forums, it might be a quality issue with the components in the sound card circuit (e.g. bad capacitors). But on the other had if they sold 100,000 units, a dozen failures isn't a huge amount.