I have a new fretless bass guitar, a new Ibanez SRF700 Portamento, with stock D’Addario Chromes flatwound strings. I am having trouble with string buzz in one specific part of the fingerboard. When I play F on the A string (8th position), the string buzzes between my finger and the nut. It sounds and feels similar to fret buzz, except there are no frets, and it comes from the nut side, not the bridge side. I don’t see any obvious defects in the fingerboard, and sighting down the neck it looks straight with a little relief.
What can I do to troubleshoot this? Do I need to adjust the instrument or my technique? I’ve found that I can silence the buzzing by muting above the finger playing F, anywhere above the 7th position, but that doesn’t seem like a practical solution. I suspect that there is a small defect in the fingerboard or string between the E and F, although I could not find one with a straight edge.
It’s difficult to pinpoint, but the buzzing seems most intense between my finger and the E harmonic node right behind it. Muting doesn’t help unless I mute between the harmonic node and the nut. If I stop muting, the buzz returns immediately. The buzz seems less if I use my pinky finger or if I barre the strings, more if I use the bony tips of my strong fingers. I suspect that using the pads of my fingers mutes the buzz somewhat. It does not help consistently enough to tell for certain.
Bending the A string away from the spot seems to eliminate the buzz. Bending the D string over the spot seems to make it buzz. Again, I can’t get that to happen consistently, so I am not sure what actually makes a difference. All I can tell for sure is that it happens anywhere within about 50–75 cents of F on the A string.
Update: I adjusted the action, which significantly changed the fingerboard buzzing but didn’t entirely eliminate it. I removed most of the relief and evened out the action. Now the A string buzzes less, and closer to the octave instead of the F. Based on my research, the buzzing might move around more, and get better or worse, depending on the exact setup and environmental conditions like temperature and humidity.