I have a Powermac dual 1.8ghz G5. OS X 10.4.10

I have been installing it in the house ready to take out into the studio. - No problems what so ever.

Took it into the studio and there is a high pitched buzzing sound coming from the actual unit - with no audio connected, internal audio turned off. So it must be coming from the physical unit.

It sounds like digital noise, everytime the screen changes or I move a window on the OS , I can hear it clicking/buzzing in time with the on screen movements.

The only thing I have connected is my Edirol FA-101 via FireWire and it has its own power supply..... If I set the CPU usage to low. No problem, Set it to high ( as it should be in the stuido ) I have the buzzing noise.

If I disconnect the edirol I do not have any problems.

I have read of the G5 buzzing, power supply issue. Any of you think this could be it ? - And the most important part...WILL THIS DAMAGE MY MAC ? - If not I can live with it... But why would it get worse with the FireWire interface plugged in ? - Also be aware the output from the edirol is not connected to any monitors so it cant be audio interference I am hearing..

Sorry for the lo n g post.