I've read previous posts on this subject and it's seems to be quite common. I've just got a Velodyne CHT10R which is just fantastic but I also have a hum which I couldn't hear before. As I hadn't got a sub before I'm assuming I couldn't hear it because my Mission m70i's don't go low enough for it to be noticeable before. With the a/v amp switched off the hum dissapears. When it's on the hum is present with any source selected. Like other people have reported it's not really a problem when in use but it's enough to be noticeable on quiet passages or when sitting idle. One post suggested removing the earth wire from the mains plug of the sub but there didn't seem to be a reply to say whether that worked or not. I'm using gold plated connectors on all cables so I'm a bit stumped what to try next. Any suggestions?