Fretless bass buzz

Question

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.

Answer 1

I'll expand a bit on my comment at the request of OP. I haven't had this exact problem on any of my fretless basses but I can tell you what steps I would take if I did encounter something like this. Since you said the buzzing is coming from the nut side of the note, it might be some sort of mechanical buzz either from the tuners on the headstock or the truss rod. I had a guitar whose truss rod buzzed for certain notes, but a 1/8 of a turn to tighten the rod solved that. As for the tuners, try to replicate the buzzing and put your finger on each of the tuners to see if holding them still stops the buzz. You basically want to go over all the hardware on the instrument and make sure it's screwed in tight and doesn't wiggle. Hold/dampen different parts of the bass/neck/headstock while playing to see if you can isolate where the buzz is coming from. Also open up the control cavity to make sure nothing is loose, as a battery or some other component could be causing the problem.

If you can't find a mechanical source, the setup is the next thing you are going to want to dial in to make sure the action, bridge, and neck are all adjusted properly. I won't go into too much detail on this because there is a lot of good info out there on setting up a fretless bass (here is a great guide, also check Youtube), but I'll give you some places to look.

From your update to the question, you mentioned you adjusted the action and removed most of the relief. Does this mean you also adjusted the truss rod? Usually relief is affected more by the truss rod than the height of the strings at the bridge. Check your relief first, and adjust the truss rod as needed (see the link above for detailed info on truss rod adjustments for fretless bass). Usually if there is buzzing in the low frets you loosen the truss rod, and buzzing above fret 12 you tighten (and don't turn the rod more than about 1/4 turn a day.. let it settle after each adjustment, re-tune, and check the relief until it's where you want it). That's an oversimplification but do some reading on the subject and you'll be able to figure out if your rod is set up properly or not.

The truss rod should be the first thing you check. Once the truss rod/relief is setup properly, then you move on to the bridge and work on getting the string heights correct. I usually put the strings as low as possible without buzzing, and be sure to check notes up and down the neck as you adjust the height to make sure they all sound without buzzing. There should be a point if you raise the strings enough they should stop buzzing. If not, and they still buzz even when the action is very high (and relief is correct), then it is likely a fingerboard issue.

All of that being said, if you can't find the buzz it would probably be worth a trip to a guitar/bass tech who does good work with fretless basses. You might need to have the nut adjusted or the fingerboard refinished because it's possible there is a dent or bump somewhere along the fingerboard that is causing the buzz. These are things you want a luthier or bass tech to look at, because it's not so easy to do it yourself. They can set it up for you and hopefully get rid of the buzz. Chances are the bass will play better than ever after some professional attention.

Answer 2

Possibly you are far more used to playing fretted bass, and need to press harder. On fretted, the string vibrates from fretwire to saddle, but of course, the wire isn't there on fretless. If you are not firm with your fingering, the rest of the string can vibrate as well, but maybe only becomes noticeable around that area of the neck. If it's still under warranty — probably, I hope — then a trip to the supplier would have been my first move. A fretboard problem may be detected using a ruler to check straightness at certain points.

In the meantime, damp the string/s behind the 'fret' you're playing on. It's often a good technique to use anyway. If you are using your index finger, try to find other ways and places to play the note/s in question. Become adaptable!