I have an early 2009 17" MacBook Pro. I was very impressed with it until deciding to connect my earphones. I can hear a continual background hiss that 'clicks' in when audio starts and then clicks off when audio stops (after a short while).
This may be exacerbated as they are noise-cancelling Sennheiser earphones. However I also use them very often on my iPod Touch and never notice this at all – even in the quiet at home.
I called up Apple who said to take it into a store for the staff there to listen. Firstly it's quite a trek for me to get to an Apple store, secondly I'm not sure how they could hear this given the noise in those stores, and thirdly there's no way I'm letting a complete stranger use my earbuds!!
Has anyone else experienced this and knows how to fix it? I tried posting on the Apple forums but only found "me toos" but no solutions.