I have a Quantum 5 that's buzzing, but not everywhere. It's primarily on the A string, and somewhat on the E string. It's most noticable when fretting the 2nd fret, and gets better at about the 5th fret. I can get it to go away by raising the action, but it's too high for my taste. I checked the relief and I believe it's fine. When holding the string at 1st and 24th frets, you can just fit a credit card under the string. The neck has no trussrod, so this appears to be a good thing... I suspect it's fret wear, but am not sure if I've missed anything. When I look at the frets, I can definitely see more wear on them around the problem frets, starting at 2nd fret and getting better as you go up the neck. It's also more obvious on the A and E strings at these frets (wear on G and D strings is more around the 5th fret and up, but no buzzing here). I also don't know whether I need someone with experience working on graphite necks to do any fret work, or if it's the same as a wood neck. One final thought is that I have tapered core strings on it (with appropriate bridge height adjustment!). They're GHS Contact Core Super Steels, and the sizes are 45-65-85-106-130. I'd switch the strings if I thought it would help, so suggestions are welcome here, too. I do like the tone of the tapered cores on this bass, though.