Help me fix this "buzz"?

Here is a problem that I haven't run across before. I have a Reckhorn B-1 bass control box that is producing a "buzzing" noise through the speakers. I did not notice this noise when the device was new. The box is small and tightly packed. Because the noise is in both speakers, I suspect a power supply problem. The PS is a standard EI core transformer to a bridge rectifier to (2) 2200 uf, 16 v caps to 7812/7912 regulators. All tightly packed together, with the caps right next to the transformer. If I push down on or grasp the PS caps, the "buzz" disappears, leaving a low level hum, much fainter than the buzz. So what is going on? Are the caps damaged? Is the transformer coupling noise through the caps? I am thinking of replacing the caps and mounting the transformer in a separate box, but I would like to hear any ideas from my homies before I start tearing things out.