Peavey bandit 112 buzzing and hissing?

For some reason, this one has started buzzing and hissing like crazy when I play a C note on the low E or A strings. It's done this with all of my guitars, so it is definitely something wrong with the amp. It's a solid state. it wasn't buzzing when I bought it, and I've been trying to figure out why it's been buzzing with no luck.