Humming from iMac headphone output after 30 seconds of no audio playback

Thanks RRFS,

RRFS wrote:

I don't think this is a feature. It would appear that you have a ground fault or a component failure. If the ground on your wall receptacle is proper you should not be getting the A/C hum unless a filter component in your iMac has failed. Even if you have to use a 3 wire extension cord try using a different outlet and see if the problem continues.

But surely the humming would be constant if there was a ground fault or a componant failure?

When any audio is playing, the humming is not present. After 30 seconds of no audio the humming starts. When you play any audio from any program the humming stops a fraction of a second before you hear the audio.

This is what leads me to believe it is some sort of setting - maybe power saving the way I remember some USB ports turn off power (I used to use PC's until only recently and knew how to stop it happening) I don't know whether Macs do this as well?

PS - I know faults can occur at any time but this iMac has only been out of the box for a few weeks! 😕

RRFS wrote:

Since you say it's only been out of the box for a few weeks, have you tried using your 90 day free phone support?

Yes, got a support call scheduled for Tuesday so watch this space!

🙂

Apple phone support couldn't find a solution. They recreated the problem while I was on the phone with one of their iMacs.

The guy on the phone was very helpful and said he would get in touch with the engineers and get back to me if they have any further information. Will update here as & when...

So, unfortunately, I'm stuck with my 30 second delay hum for the forseable future 😟