Fretless Buzzz 7th Position/Fret on A, D & G

[moishelichtfuss]

So, I have a little problem:

I have a Fretless Precision Bass with TI Jazz Flats and there's a consistent buzzing sound on the 7th Position on the A, D and G String; it's definitely not mwah.

The facts: Neck is pretty straight with little relief. I can't add more relief because the truss-rod is already loose as can be (Maybe it's also a problem that the strings are pretty low tension). The neck is not shimmed.

Might it be that the neck is uneven? The problem really doesn't go away when raise the bridge saddles. (I didn't go to extremes here, but who wants that?) I can't see any irregularities just by looking at it and also wondering why it is so consistent at the same position on the upper three strings.
Again, I guess the low tension of the TIs only enhances the problem.

Does anyone have an idea? I'd be very grateful.

Another good question is of course, why the neck won't bend. At least the truss rod seems to be doing its job.

[bassgod0dmw]

It is only at the 7th position? Or do you get buzz the further you go up the neck?

Originally Posted by moishelichtfuss

The facts: Neck is pretty straight with little relief. I can't add more relief because the truss-rod is already loose as can be

I think you just answered your own question

At least the truss rod seems to be doing its job.

It would seem to me that it is not

[moishelichtfuss]

It is indeed only at the 7th position. No such issues further up or down the neck.

With 'doing its job' i mainly meant that the truss-rod doesn't seem to be broken, since its retaining neck-straightness pretty well, even with slightly higher tension strings i had on it (medium chromes, medium ghs pressurewounds).

[Turnaround]

Sure sounds like a hump in the fingerboard. Eyeballing it isn't going to tell you - you need a straightedge. Even very small dips or humps can cause nasties.

[moishelichtfuss]

So I took off the neck today and noticed that without strings it has a slight backbow. The general method proposed on this forum seems to be putting on some heavier gauge strings and letting it sit there for a day or two (with the optional half-step or whole-step up).

Maybe I should look into that problem first before I check out the fretboard further?

[moishelichtfuss]

So...just to give this one closure...

...I took the bass to a luthier who lives 'round the corner (and who already did a nice job on an old Höfner guitar of mine) and he levelled the fingerboard (apparently had to take of half a millimeter) and filed down the nut slot...eveything seems hunky dory now...action is nice...bow problem was maybe due to weather or I didn't look properly...