X220- headphone jack problem- hardware?

[vinuneuro]

Suddenly my X220 has developed a hiss when headphones are plugged into the jack.

-It doesn't vary with the volume control or whether or not muted.

-If I restart the machine the hiss goes away when the screen goes blank and comes back when Windows starts up.

If nothing is played for a minute or so, the hiss goes away (I think Windows disables devices if they're not used to save power) and as soon as something is played it comes back. Also goes away if the audio device is disabled in device manager.

-So far it seems that anytime the audio jack is supplied power it's hissing, whether or not it's muted.

Does this sound like a hardware issue? Though still under warranty, I think that would unfortunately mean a motherboard replacement. This hasn't been the most reliable machine, so far two bad screens, a bad fan, and now potentially a bad headphone jack.

[vinuneuro]

It's happening with Ubuntu as well. Guess that confirms hardware problem.

[rjwilmsi]

Simple query: have you tried disabling the built in microphone?

How loud is the hissing? Have you tried disabling bluetooth/wi-fi, unplugging any USB devices? Interference can cause these problems e.g. work laptops (generic Dell) tend to have the problem that when you move a wired USB mouse this causes a quiet but audible squeak if you have headphones plugged in.

[vinuneuro]

Hi, yea one of the first things I tried was disabling everything in the bios. No change. It's not loud at all, but if I have earphones in I can definitely hear it in a quiet room. Not only that, when Windows (?) cuts power to it and turns them back on, you can hear a crackle. It's certainly not the end of the world, but something is going on and it's pretty annoying.