I recently had a strange problem start occuring when listening to iTunes: a strange buzz noise that would sound every once in a while. At first I though maybe I had some corrupted mp3 files. I could never get the sound to repeat at the same place on a song, though.
So I did what anyone should do when experiencing something like this: think of anything you recently did that may be caused the change. For me, it was adding an external hard drive the day before. However, the external drive wasn't even connected when this was happening. Still, it seemed too big of a coincidence to NOT have something to do with the external hard drive being added.
After googling a bit, it appears that speaker buzzing is pretty common on iMacs, especially when you have a recording studio set-up with monitors and an audio interface like I do. The problem is a ground loop issue, and some people solve it by getting rid of the ground in their outlet plugs! Okay, I think I'll pass on that approach. Others buy special cables to help eliminate the problem. Others power their monitors on a different circuit. Since my speakers already were powered on a different circuit, I was having trouble even thinking where to begin on this.
Then I got lucky. I was looking at images of various cables on Amazon that were supposed to solve this problem.
Then I remembered something. When I added the external hard drive, I had to unplug my Bamboo tablet. Since I use a non-Apple mouse and keyboard, the 4 usb ports on my mac are almost always used:
- USB Keyboard
- USB Mouse
- USB Audio Interface
- USB to External Hard Drive
To make switching components easier, I used a high quality USB extension of about 2 feet so that I didn't have to reach around the back of the iMac to change components. I had added it to the Audio Interface USB cable and would swap the interface out for the Bamboo tablet, etc.
Removing that 2 foot USB extension solved all the problems. Except for having to reach around to swap USB components, of course, but that I can live with.