Originally Posted by yvesm
Our concertone hums all the time, we don't use it.
Have you had the wiring checked for proper connections? A bad ground may cause this. While you are at it, you should double check all the wiring including the quality of connections.
Lastly, as seen on other threads this could also be caused by several other electrical systems that puts a "hum" on the entire electrical system (which is in turned picked up and played by the Concertone). There are several suggestions for installing NOISE FILTERS which have solved the problem.
Let me know if you have any specific questions and what ends up solving the problem.
OR if there is still a problem after all the above.