Intonation woes

[andyman]

So, I ran into a bit of an odd issue. I bought a used J Mascis JM a year or so ago and when it arrived it was trashed. I took it to a tech to get fixed and they fixed a gouge in the fretboard, changed a fret near the nut, did some fancy minor neck shaving to improve the break angle, and then set it up. I didn't play it much due to health issues, but a few months back I picked it up and started to notice the tuning was out on the lower frets. I figured it was the truss rod shifting with the weather (as suggested by the tech) so I tweaked it and put on new strings. Since then, the EAD strings are fine, but no matter what I do with the truss road and saddles the G, B and kind of the E strings are always a few cents sharp in the first 3-4 frets. The G is the worst, being about 3 cents out, while the saddles are as far back as they can go.
I took it to the tech and he looked it over and said that even after my messing with the truss road the setup was still great, the relief was as low as it could go, and ultimately it's a problem with the design of the guitar, that this is a common issue with guitars and the best solution (without moving the bridge) is to install a compensated nut.

I understand what he's talking about to a degree - that guitars are never perfectly in tune - but this seems like a much bigger issue, no? The guitar is unplayable. The only way to have the chords not sound bad is to tune the g and b flat a few cents, but in that case open chords sound fucked too. Are the G and B strings supposed to just naturally be this sharp on a JM?
Like, these are popular guitars and I've never heard anyone talk about it being this much of an issue.

[JSett]

Pictures of the bridge, nut, etc might help.

Shaving down the neck for break angle is wild don't ever take a guitar back to that crackhead!
My initial thoughts would be that the nut is cut too high or the fret install was bodged

[jthomas]

I had a Squire strat that would not intonate for me. I took it to a local tech (nice guy) who said: If the intonation is off when you press on the strings, but ok when you compare harmonics (i.e., you are not pressing on the strings) then the issue is the neck relief. He did the set up, and it was fine. You might check that.

Also, you said the guitar was in bad shape when you got it. Any chance that the neck developed a twist? I cant know if that would louse up the intonation, but again, you might look at it.

[timtam]

Setting the saddle position based on intonation (note sharpening with fretting) on the 12th fret only sets the scale length correctly for that 12th fret. There is a small residual error that remains, which increases the further you get from the 12th fret - see graph below. Mostly it's too small for most people to notice (and of course the problems of some equal temperament intervals are superimposed on it) and also difficult for tuners to measure. But by the time you reach the low frets it can be noticeable, and it's exacerbated by the additional sharpening that arises due to the string's bending stiffness when getting the string down onto the fret - obviously worse if the first fret action is too high. The extent to which each string is affected depends on their individual stiffnesses, and their individual first fret actions. So the first thing I would look at is the first fret action - your nut slots may be too high. If that is the case and the tech instead recommended a compensated nut, I'd find a new tech.


French, M. (2012). Technology of the Guitar. Springer. https://doi.org/10.1007/978-1-4614-1921-1

[Embenny]

Does it have high nut slots? If the first few frets are sharp but the higher frets are not, that's not the kind of intonation that can be fixed at the bridge.

When a nut slot is filed too high, the string gets pulled downward too far when fretted (especially at the first fret), stretching the string and pulling it sharp.

Guitars with tall/jumbo frets are especially sensitive to this, and a deathgrip (pressing too hard on the fretboard) exacerbates it as well. Thinner strings are also more susceptible, since they stretch more easily than thicker ones.

[timtam]

I had a Squire strat that would not intonate for me. I took it to a local tech (nice guy) who said: If the intonation is off when you press on the strings, but ok when you compare harmonics (i.e., you are not pressing on the strings) then the issue is the neck relief. He did the set up, and it was fine.

You can't set intonation without a fretted note. The whole purpose of setting intonation is to adjust the string's scale length for the sharpening that occurs with fretting - lengthening its scale length at the saddle flattens it back to the expected frequency. So intonation can't be 'OK' just with a 12th fret harmonic (which incidentally will always be exactly an octave from the open string note, unless you have a bad string). The tuned open string/harmonic note is the reference - you are adjusting the saddle based on how far the fretted note is from that reference. So with respect to your tech, his assertion doesn't really make any sense.

The relief affects the overall action, so it will affect the extent of string stretch/sharpening that occurs with fretting. So conventional intonation adjustment based on the 12th fretted note (how far you need to move the saddle to set the scale length) includes the effect of relief.

[andyman]

Re: the nut, that was my first thought but the guy said the action is about as low as it'll go without buzzing. It looks pretty low, in fairness.

[Bradley-Jazz]

Re: the nut, that was my first thought but the guy said the action is about as low as it'll go without buzzing. It looks pretty low, in fairness.

The bridge could be low to give a low action but the nut still high. If you fret the string at the third fret, so it is in contact with the third and second frets, and gently tap the string down over the first fret, is there much movement before it hits the first fret? There should be *very* little clearance there. - example here

The nut still sounds to be the culprit to me. And your tech does not sound reliable.

[andyman]

Photos, as requested. Sorry for the quality - the macro lens on my phone is hit or miss, but I can try again if these are no good.









Videos with clearances:

https://imgur.com/a/FOqycWv

[JSett]

To check the clearance of the first fret you need to capo at 3rd and tap until it touches the fret, not the fretboard. That's your clearance amount.

Have you had guitars with jumbo frets before? If you're pressing the plain strings too hard towards the board then you're essentially bending them up in pitch between the nut and fret. This is always more evident in the low fret areas.

Forum member, and friend of mine, GaryPtaszek has massive hands and the grip of a gorilla and has to use really thick string gauges to stop him naturally fretting sharp by pressure alone. It can be a real issue with Jumbo frets

[andyman]

Forum member, and friend of mine, GaryPtaszek has massive hands and the grip of a gorilla and has to use really thick string gauges to stop him naturally fretting sharp by pressure alone. It can be a real issue with Jumbo frets

Part of what's bothering me here is that I wanted to use 12s, but wouldn't that exacerbate the problem even more?

[andyman]

To check the clearance of the first fret you need to capo at 3rd and tap until it touches the fret, not the fretboard. That's your clearance amount.

Whoops. How's this?
https://imgur.com/a/d6ZV4yT

[JSett]

Clearance looks okay with capo at 3rd, could come down a touch but not enough of an issue to cause big problems.

If the reason they're fretting as sharp is hand pressure then bigger strings will improve the issue. Or playing lighter with the left hand.

Your bridge looks to be utterly decked, which isn't right. Probably because the tech 'shaved' the neck instead of just doing what's been done for 60 years on these guitars and just added a shim. What he's done is stupid and non-reversible.

[Bradley-Jazz]

To check the clearance of the first fret you need to capo at 3rd and tap until it touches the fret, not the fretboard. That's your clearance amount.

Whoops. How's this?
https://imgur.com/a/d6ZV4yT

Good videos. To my eyes, that nut looks high (higher than I have mine anyway, but it depends how you play).

Something else we haven't suggested, I don't think - capo at first fret and tune up. If it now plays in tune, the nut is the problem, one way or another. It's also possible I suppose that the nut is cut so that the string is not sounding off the front edge if the slots are cut poorly, so making the string length longer. It would quite probably buzz at the nut too if that was the case.. Either way, try the capo.

EDIT - agree with Johnny about the bridge. You can still shim it to lift that up, but there was no reason to shave the neck down.

[andyman]

What kind of issues will the shaving cause, overall?