Some amps have a reverse polarity ground switch, if it does try clicking the other way. Also, if you can, flip the 2 prong adapter and plug it in the other way, I had an old light rack with wonky wiring that would shock you unless all of the lights were plugged in the “right” way.
does the buzz go away or diminish if you lay your hand on the strings? That would indicate a bad ground in the cord. An old or crappy cord is notoriously famous for this, that’s why I buy the best cords that money can buy, with an over the counter guarantee. My best cords cost over $130 for a 20’ cord, but they’re well worth every penny.
