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Need Help - Nut or intonation woes

Discussion in 'Hardware, Setup & Repair [BG]' started by loner9, Mar 31, 2013.

  1. loner9


    Sep 18, 2010

    I have a Carvin LB 75 (5 string) that is 13 years old that I am very fond of. I have noticed when tuning that my open strings, when tuned perfectly, do not match my fretted notes, which turn out sharp up to the 5th fret, then flat on up the neck progressively.

    For example, open A is tuned perfect. When I fret the first fret, the Bflat is slightly sharp. Still on the open A, I fret the notes one by one up the neck. When I get to the fifth fret, the note (d) is perfect. As I continue fret by fret up the neck, it gets slightly flatter each time. By the time I get to the 15th fret on the A string (c) is VERY flat. And everything gets flatter as I continue up.

    I feel my intonation is almost perfect, as my open string and my 12-fret harmonic are almost perfect.

    It did have a new nut on it, could that be what's causing the problem if it was installed poorly?

    Please help! Driving me nuts. Thanks in advance.
  2. If the nut slots are too high it can affect your intonation. The first five frets being sharp points to that being the culprit. Make sure you are checking your intonation with a tuner, however. Things can sound good to our ears, but actually be way off when it comes to electronic measurement. I would check the bridge intonation first with a tuner, and if the symptoms persist, take it back to the tech who did the nut work and let them take a look.
  3. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    First off, intonation should be a match between 12th fretted and 12th harmonic, not open string and 12th harmonic which will almost always match. Some other critical measurements & proc's:

    *Set your witness points at the nut and bridge first. Nut slots should be clean, cut / angled correctly.

    *String / 1st fret clearance should be .003-.005" when fretting the 3rd. Feeler gauges are $4 at Pep Boys...splurge!

    *Relief should be .012-.014" at the 8th fret with the string fretted at the 1st and last frets. There are variations on this but I'm just trying to keep things simple.

  4. JLS


    Sep 12, 2008
    Emeryville, Ca
    I setup & repair guitars & basses
    Intonation is a whole lot more than getting the fretted note at F12 to match the harmonic, as you are discovering...
  5. 20db pad

    20db pad

    Feb 11, 2003
    I been everywhere, man...
    None. At all.
    Intonation on a string is important, but you ultimately can't fret notes on your neck, check them on a tuner, and have them ALL be perfectly in tune as you check them. The fretted notes will all be a tiny bit off due to the temperament system that the Western world uses for division of the octave.


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