I bought a new Fender Rumble 75 a couple of months back. I use this just for practice. The amp has some pretty annoying rattles and buzzes at certain settings and at certain notes. I don't believe it is the speaker itself but rather a peaky sort of resonance in the case. I took the grille off and that had no effect. It took it back to GC and we compared it to some other identical units. They all had similar rattles and buzzes. GC offered to exchange it or take it back but since they all did it I decided to keep it and try to do something about it. I does sound pretty good with my basses other than the rattles. The volume is set at 9:00 o'clock. Not very high. I plug in my active bass to the active input (reduced gain). My question is has anyone else experienced this? If so, were you able to do anything about it? Stuff it full of insulation, put some extra ports in it, plug the port, replace the speaker, etc.? I don't need a lot of volume. Just for practice. But I would like a clean sound. I go direct for recording. Thanks and Happy New Year.