The buzzing is caused by the points in the regulator opening and closing at a very rapid rate more than normal probably due to the voltage sensing circuit for the alternator. This would be the blue wire to the alternator and the red wire from the regulator to the soldered junction. Or you may have just gotten another bad regulator.
Silly question: did you re-install the regulator using the little rubber washers? I know, but I have to ask.
A very good option would be the solid state regulator made by Wells which is sold at Napa and Autozone PN. VR 715 for pre 73 GM vehicles. Here is a good thread on another forum about it.
http://www.chevelles.com/forums/45-c...-60s-cars.html