Hi all... Why, do you all think might I be encountering the following; When the tone of a '51 style P bass is all the way open, the bass is quiet. When it is rolled all the way back, it hums, unless I touch the strings.When i do, it stops humming. My guess is that there is an earthing issue somewhere. What I do not understand is the difference, depending on tone knob setting. What might be the reason for this? This is a passive single coil-equipped instrument. Thanks!