In all fairness to the reputation of the amp builder, I think it would be considerate to prove that your house wiring, and/or your electric power source is not contributing to the hum. I have witnessed some strange things with electrical circuits over the years and am really curious about the cause of your hum. In the 2 weeks since posting to the public on this forum, have you carried your amp to a friend's house during this time to compare? Sometimes the process of elimination is the only way to realize what is or is not causing a problem.