Is it possible to play through a tube amp like, say, a mesa boogie bass 400+ if it doesn't have its full complement of tubes? I read a user review somewhere in which someone claimed to have run the amp with just three or four tubes, though it obviously didn't sound too good. If just one or two power tubes are missing, will the amp run at lower wattage or place extra strain on the remaining tubes? My guess is that running it with a blown tube is less dangerous than running it with a tube that's not there at all. I just bought a bass 400+ used, and it's in need of retubing but I'd like to verify whether it works at all before I bother to retube it.