The other day I picked up a Sunn Coliseum bass head, to my excitement. Got it home immediately, hooked it up to my Sunn 2 15" cabinet, turned it on, and... Bwrrrrrppphhhh. It sounds... Like a fart. And it's not very loud, at all, for a 500w amp, even a solid state one. Playing my guitar through it, it sounds absolutely fantastic. But when I plug in my bass, it sounds very trebly, does NOT get very loud at all, and any low end tone simply sounds like, well, passing gas. Is it just due for a routine maintenance? Am I dealing with a whole different beast from the 200S and 300T that I'm accustomed to? What should I do?