Thanks for the input Scott.
So I'll have to look into installing some kind of liner for the rear brake cable. That seems like the only possible way to get rid of the road buzz. Given how stiff this bike is, unless you are riding on freshly paved roads it would seem there is always going to be annoying buzz. I can't believe you put up with that for 15 years, you must really love the Quantum. By the way, what kind of tires and pressure do you use? If I am able to cure the noise and decide to keep the bike, am considering moving to 25c tires from my standard 23.