Macbook with horrible noise issues when connected to power

Hi all,

Before I get into this, let me just say that my Early 2011 MBP 15" has had a good life, and may have suffered a couple too many drops over time!

I have tried to research this topic as much as I can, but now need to ask in regards to my specific situation.

The main problem is when connecting the magsafe power, any audio output emits an absolutely horrid buzzing (earth) noise. Now before you jump to any conclusions, from my research I can tell you the following points:

- It is not the charger itself. I recently purchased a new genuine charger (with 3 pins) and have the same problem.

- It is not the power in my building. It happens wherever I go.

- Volume control does not effect the level of the noise.

- The noise generally does not come through the internal speakers (though sometimes has) - however, ocassionally when playing sounds such as system sounds, the speakers will click mid-sound and the sound will stop. Playing music for example through iTunes is fine though.

- It is not only coming out of the headphone output, but the output of ANY other audio device attached. I also use a firewire audio interface and the buzzing also comes through that. There is a buzzing sound also evident on any input channels when recording through the interface while the charger is connected.

- Certain operations throught the Macbook will make the noise fluctuate.

After doing some research, I found out about the grounding pins on the main board that are supposed to come in contact with the bottom plate of the Macbook. Taking a look at these (there are many - maybe around 10?) - one of them that is situated above a USB input is damaged and has been pushed in - therefore will not come in contact with the bottom plate.

So I guess my questions are:

- Is this broken pin likely to be the cause of the problem?

- If so, is it an expensive fix?

I'm sure that Apple repairs would be a costly experience, I'm just trying to weigh up if its worth forking out for the repair or now may be the time to take advantage of upgrading.

Thank you all for your time!

Dylan