Well, my Hartke HA2000 has arrived. The good news is I like it's tone. The bad news is it has a very loud fan, and what appears to be a healthy ground-loop hum at the output. This model has 2 1/4-inch speaker outputs, and they show signs of corrosion. I can't be sure that this is the only source of the hum (have no cleaning supplies currently). Has anyone else had similar problems?