I'll try to keep this short. After shielding the hell out of the tank yesterday and putting it back in the bag, no change. I went to bed frustrated. When I got up this morning I flipped it on. Lo and behold it was quiet as a could be. No hum, no feedback squeal with just a tad bit of hum on 10 which is normal. I played with it most of the day and it was great. I'm totally stumped. Maybe it's some sort of interference in the house. The new MOD tank showed up today. It is identical in EVERY way to the Ruby...right down to the rivets. MOD is either a rebranded Ruby or the Ruby is a rebranded MOD. I installed the MOD with no shielding and no bag. Just plugged it in and put it on the floor behind the amp. It too was completely quiet and no feedback. I played it for an hour and it sounded wonderful. Right toward the last it started with a little hum on 3, and it did feedback, but on 10 instead of 6. This problem is intermittent. I don't get it. Just doesn't make sense. I get plenty of verb on 3 and 4, and the hum isn't terrible. It's acceptable and sounds vey nice. I'm just going to live with it and try to forget the $23.50 + shipping I wasted on the new tank. No toothpicks @Wally. Thanks for the help gentlemen.