I have a fender pj, 4 string. It has 500k vol, vol, tone pots. It's been my fav for the last year. Recently I changed strings, I tried some EB cobalt's.... I didn't like them so I put my bass boomers back on and now it sounds zingy. I thought maybe it's the nut? I looked at my fender Jazz which has the same neck and everything seems ok. Anybody explain why I'm getting this zingy sound?