Hi, I recently purchased a Fender FSR Standard Jazz Bass and Fender Rumble 15 amp from GC. The bass plays like a dream and the amp is fine, EXCEPT that it seems that I get a lot of hissing through the amp when the tone control is turned up. It goes away only when I'm touching the strings, bridge or input jack. I've done a little googling and it looks like this isn't an uncommon problem, but does anyone know what the solution is? Or why this actually happens? Any advice would be much appreciated, thanks.