7th fret problem

Hi all from the new guy! I have been learning from this forum for a couple years and my membership application was recently accepted (thank you gracious moderators)!

My mando intonation is out on one note. Only one note... G string 7th fret. Even using a tuner I can’t really see if it’s sharp or flat but it’s not in tune with the adjacent D course... I hear a slight dissonance, limited sustain, and it just doesn’t ring like the other notes.

For context, I replaced factory nut with bone and re-fretted with EVO. Nut slots are carefully filed as low as I care to go and using a fret rocker I can’t detect any high or low frets... I am stumped. Ideas?

The mando is Eastman MD315. Since new frets, nut, setup, etc it is a real cannon. Especially on the E and A strings.

Sorry I can't help, but did you have this problem before the refret?

Good question! I honestly don’t remember. The new larger EVO frets made the instrument so much better... I found the original small frets very difficult to get a clean note from so I likely wound not have noticed. The new frets help with tonal quality of all notes except the 7th fret dud!

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Originally Posted by PG Pickin

but it’s not in tune with the adjacent D course... I hear a slight dissonance, limited sustain, and it just doesn’t ring like the other notes.

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That is three distinct things; I know your question is about it being out of tune, but also not every note on a given instrument is going to necessarily be as strong (or weak) as another one. Since you don't seem to have any issues with the other strings, it is unlikely that the fret placement is off. I have an F5 that I find I have to tune the G very slightly flat for it to play in tune in every position. If the action is too high, or there is any flaw on the 7th fret crown, it could cause a problem. For sure try a new pair of G strings just to remove that from the equation. You might have to ramp the saddle back a hair as well.

Simple. Just need to move the bridge slightly.

Attachment 182925

I have tried moving the bridge position but the intonation problem between G and D strings remains apparent at 7th fret.

What I did notice is that there is a slight twist to the bridge; the bass side (at bottom of drawing) leans closer to the neck than the treble side. I think this could be the culprit.

This weekend I am going to remove the bridge, soak in hot water, and see if I can straighten it.

You could simply angle the foot to help. If that is not enough I would not soak the saddle, but instead cut some wood away to take the string back to where it needs to be.

Thanks Pops1 - I have tried shifting the bridge position but it throws the intonation out on the other 3 courses. I will fiddle with it this weekend but is seems like something funky with the bridge may be to blame.

Quote:

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Originally Posted by PG Pickin

...Even using a tuner I can’t really see if it’s sharp or flat but it’s not in tune with the adjacent D course...

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That's why I'm stumped on this one. If a tuner cannot detect an intonation problem it just doesn't make sense that there is one. I can't think of any physical problem with the mandolin that would cause one string to be out of tune at only one fret and the error be undetectable using a tuner.
Probably best to take it to someone who is expert with mandolin set up to analyze the situation.

I appreciate all the suggestions. The main reason I do the luthier work myself is because I live in the boonies and I have had a guitar butchered by a local “professional” once in the past. I am going to have a closer look with a high-sensitivity tuner this weekend. My hearing isn’t that awesome but I am particular about setup and there is definitely something off.

There’s a good Wikipedia entry “inharmonicity” that might relate. My take is that the spectrum generated by two different length, mass, plucked strings is different, even if the fundamental (what the tuner measures) is the same. One particular note, on one fret could have a tonal content not seen on other notes, even if the rest of the instrument was somehow linear in response, which it isn’t . Perhaps a different string type might alleviate the problem.
Good thing I don’t have a good ear!

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That's why I'm stumped on this one. If a tuner cannot detect an intonation problem it just doesn't make sense that there is one. I can't think of any physical problem with the mandolin that would cause one string to be out of tune at only one fret and the error be undetectable using a tuner.

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Yep, I was stumped as well when I had a similar problem on a guitar. Solved it by changing strings, so the suggestion above to change to a different string type is a good one.

wondering if there is a very small flat spot on the string(or strings) at that fret-wondering if it might register correct with a tuner, but give you a strange note quality you are hearing. +3 on changing the strings. I would take a good look with a magnifying glass of the fret in that area. Maybe take some steel wool and buff it really well. just some random thoughts.

keep us posted on the outcome
d

I have also cured problems with a string change. I would at least change the offending string first before doing anything else.

Something quick to try is to tune the instrument down a semitone and then see if the problem changes.

If, for example, it moves from the 7th to the 8th fret then you know it's neither the fret nor the saddle. Probably something to do with how the instrument reacts to a particular note.

If it goes away completely, this might indicate a defect in the string over the 7th fret which will have moved slightly away from the fret because of the detuning.

If nothing changes you haven't learnt anything, but it's a quick and non-invasive thing to try.

Since you say a tuner shows neither flat or sharp on that fret then it sounds like intonation is not the issue. My guess is the dissonance on one particular note is something ringing in resonance. I would suspect strings between bridge and tailpiece, strings between nut and tubers, loose hardware tuners, tailpieceetc etc. IMHO
Dave

One more vote for changing strings.....you could try a different gauge as well.

Also check the slots on the bridge saddle.
If the saddle is leaning forward slightly it may not have a clean contact on the leading edge and could cause the symptoms you're describing.
A couple of strokes with a nut file to increase the break angle could fix that.
Odd that it would only happen at the 7th fret though...

Thanks for all the great input. I chased this issue from tip to tail... straighten twisted bridge and re-ramp string slots / new strings / crowned fret #7 / fixed buzz at tailpiece / nut inspection / de-tune / adjust bridge height / adjust neck relief... none of this made any difference that I could detect. However I did see that fret #5 was a hair high so I levelled the whole neck and re-crowned. I can’t say that the issue is 100% gone but the sum of all this work is that it’s not nearly as annoying as before. I am going to live with it for now.

The Eastman is a nice mando... even compared to my Northfield the Eastman stands up. I have enjoyed working through all the setup tweaks and the instrument finally feels like mine; very different than when I first picked it up. I appreciate all the input that you have provided. Cheers

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Originally Posted by PG Pickin

I hear a slight dissonance, limited sustain, and it just doesn’t ring like the other notes.

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It could just be a "wolf tone" on that particular instrument.
Sometimes and instrument has one particular frequency that gets squished for whatever reason.

since you've done all you mentioned, I would consider pulling the 7th fret and replace it. While doing that of course, really clean and inspect the fretslot, glue in the new fret also. if it were mine and everything else seems to check out, I would do it.
d

After all the troubleshooting, I agree with CWRoyds this could be a wolf tone. There is a subtle and intermittent WT on the E string... could be the same thing at 7-th fret G string. When picked the note goes flat momentarily then after ringing very briefly it returns to pitch.