Originally Posted by scatman
I forgot to add: the hum would "stop" when I press my hand on the cable, at the bass input. (one of those "perpendicular" Monster Cables) But I need to play, so I can't keep my hand there! Any thoughts on that?
When you ground yourself to the cable connector you are doing exactly the same thing that conductive strings and a bridge ground wire do automatically. The difference is that you can play while touching the strings but not with one hand on the cable connector!
Your options remain:
1) shield the bass better, it will help but not in every case
2) wear an antistatic bracelet connected to the bass ground
3) put some grounded metal on the bass somewhere where you can easily stay in contact with it while playing
In many cases the noise is not loud enough to interfere with playing, it just sounds bad during quiet periods between songs. If that is the case there is a fourth option:
4) turn the volume down between songs or keep one hand on that connector when you are not playing.