Luke 2 strange harmonic issue

[Craiguitar]

Hi all,
One of my Luke 2's has this strange issue with a harmonic that always occurs. I can for instance play a muted chord, then as soon as I release my right palm off the strings, on comes the harmonic. It only occurs on the D string. The harmonic would normally only physically occur played on the D string between the 9th and 10th frets. However this happens all over the neck.

I don't think the bridge is the issue, and it's definitely not the cavity springs. I was wondering if it was the nut? but I can't figure it out.

Has anyone else experienced anything similar?


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[ksandvik]

Could you check if one of the frets is too high or has grooves?

 

[Craiguitar]

You know what, I never though of that! Thanks for the tip..
Placing a flat rule on the neck it's possible the 10th fret is tad high, but barely noticeable. Could this be the cause?
They are (unusually for a Luke) Stainless Steel frets. So I know they are harder to work with. My local tech is going to be unhappy to see this turn up on his bench.

 

[DrKev]

I have some thoughts...

1) Not a high fret causing this. Nope.

2) When the note is ringing out, very carefully touch each string in turn to figure out which one is actually causing the note. Check the string lengths behind the nut too. That harmonic has a node point 3 1/4" from the D-string saddle. That suggests that your picking hand may be doing it (in whichcase vary your picking hand position and see if goes away). But the length of A string behind the nut could also be the culprit.

 

[Craiguitar]

I have some thoughts...

1) Not a high fret causing this. Nope.

2) When the note is ringing out, very carefully touch each string in turn to figure out which one is actually causing the note. Check the string lengths behind the nut too. That harmonic has a node point 3 1/4" from the D-string saddle. That suggests that your picking hand may be doing it (in whichcase vary your picking hand position and see if goes away). But the length of A string behind the nut could also be the culprit.

Hi,
It's definitely the D string causing this. Once it starts ringing, if I dampen the D string, it stops.
I can confirm it's definitely not my picking hand because it doesn't happen on any other guitar (including my other Luke's), or on any other guitar I have ever played, period.

I might need to take it to my tech anyway to see if he can diagnose it.

So if it's not a high fret, and it's not 'me', then what else could this be? I was initially wondering if the nut was somehow cut wrongly and that could cause the issue?

 

[Daniel]

Hi,
It's definitely the D string causing this. Once it starts ringing, if I dampen the D string, it stops.
I can confirm it's definitely not my picking hand because it doesn't happen on any other guitar (including my other Luke's), or on any other guitar I have ever played, period.

I might need to take it to my tech anyway to see if he can diagnose it.

So if it's not a high fret, and it's not 'me', then what else could this be? I was initially wondering if the nut was somehow cut wrongly and that could cause the issue?

Hi there, If there is a burr in the nut, or it was back slotted then it could cause some ringing issues, however, you'd most likely have intonation problems as well. Have you changed the string gauges on the guitar from the stock 9-42?

 

[Craiguitar]

Hi there, If there is a burr in the nut, or it was back slotted then it could cause some ringing issues, however, you'd most likely have intonation problems as well. Have you changed the string gauges on the guitar from the stock 9-42?

I'm leaning towards thinking it's the nut. For instance if I capo the 1st fret, then play, the issue goes away.
No I haven't changed gauges, I always go with 9-42.

 

[SilosRock]

I had a similar issue with an older Silhouette of mine. I just had to replace the string causing the overtone. Check to see if the string is fraying. Once I put new strings, it was good to go! Good luck my friend

 

[SilosRock]

Do you use coated strings?

 

[Craiguitar]

I just use regular RPS super slinky’s. I change them every couple of weeks so there is no reason to suspect that the string is an issue.

 

[Sosomething]

If this hasn't been solved....

My money is on the nut. I think the harmonic you're hearing is actually the D string ringing behind (above?) the nut. I've had a number of guitars where this happens. It's usually because, well, nut slots are a tricky thing. You need them open and smooth enough to not bind the string, but even a tiny bit TOO open and they don't stop string vibration between the nut and tuning pegs when you play.

Luckily you can diagnose this in 5 seconds.

Play the way you do when you get the weird harmonic. Then take your finger and just lightly place it on the D string above the nut. Does it mute the harmonic? If the answer is yes, that's your huckleberry.

There are 2 solutions to this if that is the case:
A.) wrap electrical tape stick a wad of foam around / under the strings above the nut to mute them
B.) Have a luthier make and install a new nut on the guitar

 

[SilosRock]

Hopefully you solved the issue. I know my previous statement sounded silly as I change my strings frequently as well. A few weeks after I used coated strings (for the first time) this issue arouse. There was the slightest bit of fray or lack of coating possibly above the neck pickup where I usually pick. Changed the string and I was good to go. Good luck!

 

[Craiguitar]

Thanks guys. I’m going to play it safe and let my local tech look at the issue. I know he’s not a fan of compensated nuts and will Probably give me a lecture about that, but if he can fix it, then I’ll be okay with that.

 

[Craiguitar]

Update: SOLVED!
OK, just thought I'd update on this for future reference.
My Tech fixed this issue. It was (as I initially suspected) related to the nut.
The issue was that the nut is cut in such a way that the D string sits properly in its slot at the zero fret point but behind that instantly breaks away, so it wasn't sitting on the nut for the entire width of the nut. Such is the shallow break angle of the strings on this design of guitar, that this created a resonant frequency which was travelling from the headstock side over to the playing side, and being amplified by the pickups.

The issue is fixed by slightly building up the rear end of the nut slot (on the headstock side) so that the string sits on the entire slot of the nut, not just the first part of it.

My Tech said that, it's not that the nut was badly cut, but an inherent design risk of guitars with shallow string break angles, that fine margins come into play, and the chances of a resonant frequency from the strings beyond the nut is always there, and some players (or listeners) may not have even noticed there was an issue at all. Nevertheless, it was there, and not just imagined by me!

 

[DrKev]

Hooray! Glad it's all fixed!

Yes, cutting nut slots for the D- and especially the G- string can sometimes be a very finnicky business, especially on a strat-type headstock where the angles are even tighter.