Anyone has the same problem? Every time I plug in my headphone, I can hear a small but weird hissing noise in the background. It will go away if there is no sound output for a while (several seconds).
From what i have been reading, its a common occurence in MBP's on the Santa Rosa platform. The solutions seem to be getting a pair of higher impedance headphones, or get a Digital to Analog Converter and use the Optical out that comes with your MBP.
I have the same issue as well. I've tried many different things testing it. The issue appears to only be in Leopard, I'm hoping this gets resolved by Apple.
I'm pretty sure this is a driver issue, not a hardware issue. Meaning, there isn't a fix for it. I tested this on 3 different machines and all of them had the same noise. I doubt you getting a new one will solve the problem for you.