My rig consists of a Furman tuner/power conditioner, Crest CA-6, and Demeter HBP-1. I have owned the Demeter pre for less than a year now but I will be replacing the tube again for the second time. The preamp is very noisy until I change the tube. But then after a couple of weeks or so, it becomes noisy again. What could be the problem? I carry it to church every Sunday, so could transporting it cause the problem? I try not to bang it around much, but it occasionally happens.