Thanks for the questions... I do sense a familiar way of systematic thinking.
Yes, I am sure it is the pick AND the pickup. No it is not the string. At some point I carefully hit the pole-piece forcibly with my pick without touching the string and again I got the "clack!".
No, it's a plastic 3mm Jim Dunlop "Big Stubby" pick.
No. It does not happen when I play fingerstyle.
I know, but I like to associate the two. For, pretty much, all of the other styles I play with my fingers.
I don't think that would help.
Applied and Engineering Physics Rulez!
Thanks man...
