Strange notes when fretting strings

[manicbassman]

I'm getting strange notes occurring when I fret the strings on my acoustic bass above the 7th fret... They're even being picked up by the bridge transducer...

I find that if I use a spare finger to lightly mute the portion of the string above the fretting finger the note dies... so it appears the string above my fretting finger is vibrating.

I'm not sure if the string above my finger is actually making contact with the fret above or not, but I suspect it is as there's no perceptible give when lightly pressed. I'm consciously trying to fret as close to the fret as possible without being on top of it and choking the note.

I'm not getting any fret buzz at all when playing, so the relief and bridge are correct. I've checked the string heights and they're the same as listed on the QA card that came with the bass.

The bridge is not adjustable at all (without going to a luthier) so the only adjustments I can make are changing the strings and/or slackening off the truss rod slightly.

Tonight, I'm going to try an eight turn anti-clockwise to see if it helps or not.

[XylemBassGuitar]

Originally Posted by manicbassman

I find that if I use a spare finger to lightly mute the portion of the string above the fretting finger the note dies... so it appears the string above my fretting finger is vibrating.

When you say "above", do you mean the string is vibrating towards the headstock, behind your fretting finger?

If so, loosening the truss rod an eighth of a turn like you mention should probably help. This sounds like a case of "back buzz" where the string vibrates against the frets behind your finger, and not in front towards the bridge side. Loosening the rod will add a little relief to the neck, giving the back-buzzing string some room to vibrate freely.

It's very odd that the transducer is picking it up though...

If I've misunderstood your description of the string vibrating towards the headstock behind the fretting finger, my apologies.

Let me know how it turns out.

[manicbassman]

that's precisely what I meant. The string part towards the headstock is being set vibrating by the action of fretting... it's quiet, but very disturbing to me as it's dischordant to the note I'm actually playing.

The transducer on this bass is amazingly sensitive...

Loosening the truss rod an eight turn had no effect other than me being able to pluck harder without normal buzzing.

I shall be exploring things further.

[XylemBassGuitar]

Since the truss rod adjustment didn't improve the situation, you should try shimming the nut. This will raise the strings behind your fretting finger up off the frets and should eliminate the buzz.

You can take the whole nut off and glue a thin shim to its underside, or you can shim each string slot individually by placing a small piece of matchbook cover under each string that's buzzing.

Finally, you could also just get a replacement nut.