I play a thumb so I am familiar at least, aside from that I want that bass, and have been eyeing it for a while now..
anyway...
how long ago did you buy the bass?
how old are the strings?
can you or did you have the neck looked at?
jmx is right, otherwise maybe the neck pup is too low?
i dont suggest messing with the string spacing now.
on which pup are hearing this problem... or is it both.
jluv
