The smoothing caps aren't of a high enough voltage rating and over heat. The buzz is the first sign of failure. If left, the loading on the bridge rectifier ( ac-dc convertor) causes failure of one or more of the diodes which, if you are unlucky, will take out more of the components. My wife had one and it died very quickly from the onset of the buzzing. I had it in the workshop and found that most of the chips had fried. Solution is, as others have stated, to up grade the caps to a higher voltage. As soon as you hear this buzz, pull the plug and have it checked.
For more info on Logik see http://en.wikipedia.org/wiki/Logik
Phil Smith
August 2011