Ive got a Ashdown Mag300h head I think its called. Well anyways, I went to band practice and everything was EXTREMLEY low volume and couldnt get as loud as it used to. And it only works in my High input and not in my low. Is my head blown? I dont think its my cab because I hooked up my bass-vamp hoping to use it like a pre-amp so I can at least get some volume... but does anyone know whats wrong?