A friend of mine (and pupil) came to me today with his amp and asked if I knew what was wrong with it. -It's an Ashdown Electric Blue 150 combo. -Unplugged and plugged it gives a hum (not very loud, but not a "normal" hiss or pup interference either), that doesn't change if you turn the knobs (ie it doesn't get louder if you turn the volume knob). When you play the bass you hear a very silent amplification, but nothing more than that. -He didn't blew the amp, it worked perfectly one day and a couple of days later it gave this hum. He also told me that the amp had been moved by people without his supervision. They told him that nothing happened to it, but I doubt that they would tell him that it fell after he told to them that it was broke. -I took of the grill and had a look at the speakercone, which wasn't ripped. My guess is something happened to it during transportation. What's your guess?