I have a spruce top Kayla u bass that I bought used. When pluged in the E string had very little volume to the point it was unplayable. I did Google searches and found others that had the same problem but couldn't find a solution that worked on mine. Everything from amp setup to replacing the strings.I wanted to sell it but didn't want to stick someone with my junk. So after it sitting for six months last night I said what the heck I know its the same all the way down the fretboard so it has to be the saddle or the pickup so I took off the strings and removed them. I tried filing the saddle center back toward the nut a little restrung it nothing. Then I pulled the saddle off the pickup that's when I thought oh well I guess I'll buy a new pick up because all the shims fell out and I thought I'll never get this ($/,!@ thing back together. After I chilled for a little while I went back at it. I figured it didn't work like it was before so the only thing I could do different than before was to turn the saddle 180 degrees. I put it back together restrung it pluged it in and it's is perfect !! I don't know if it made any difference by the saddle being that way or that one of the shims wasn't in the right place , if you take one apart you'll see what I mean but it fixed it. As much as I was aggravated by this I had to share this hope it helps someone else. Thanks ricky