Repair of guitar - what needs done?

Construction and repair of Classical Guitar and related instruments
simonm
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Re: Repair of guitar - what needs done?

Post by simonm » Wed Jul 26, 2017 10:45 am

To be honest, I can't see any issue with the way the strings are tied. They look very neat to me. I would be interested in hearing what people think is the issue with theses knots.

Assuming that the 630 model is a 630 scale the length from the nut to the 12th will be 315 as others have pointed out. The length from the 12th to the theoretical position of the front of the saddle will be 315 giving a total of 630. After this compensation is added. This is partly a matter of "taste" and partly something that can be calculated scientifically. (Check out Trevor Gore's books if you are mathematically inclined).

I don't know whether it is due to the photograph angle or whether it is real, but in your picture if looks like the saddle is skewed slightly making the bass slightly longer and the treble slightly shorter. This is quite typical. 2mm is about the maximum compensation commonly used on 650 scale guitars. So with a skewed saddle it might be 632-ish at the bass side and 631-ish at the treble side. Or it might turn out to be 630 and 631 respectively. In short 0-2mm is probably well within the "normal". On a relatively short scale guitar I would expect the compensation to be a bit less than on a 650 or it could be absent. Strings play a role here too.

How is the person tuning the guitar? If the person is a beginner and relying on a tuning app, then the problem might be more the person than the guitar. There is a master class on you tube whether the teacher takes a guitar off the student and tunes if for him and comments while doing - "you can never get a guitar into tune, all you can do is get it less out of tune". The point here being that a beginner relying on an app may not realize that the goal is to get the guitar "less out of tune" rather than to get the guitar in tune. :-)

Peskyendeavour
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Re: Repair of guitar - what needs done?

Post by Peskyendeavour » Wed Jul 26, 2017 12:17 pm

Thanks for all the above, very helpful checks. I'll do them next I visit.

She's a violinist so she tunes by ear, as do I. (She's perfect pitched, I just tune the strings relative to each other and that's fine for me) we just used the gadget after discovery of the problem to check - for my own sanity that I'm not dreaming it...

What happens is we try to tune the strings as we would normally, then while playing a tune or scale, some notes jump out at us as out of tune... Seems really odd to me, not all of the notes on the same string is out or anything consistent like that, so I really hope it's not (some of the) frets. Though I visit other people's houses with guitars often, I'm still quite new to this, I don't know that many guitars with problems, and certainly haven't come across this issue before.

SteveL123
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Re: Repair of guitar - what needs done?

Post by SteveL123 » Wed Jul 26, 2017 4:19 pm

simonm wrote:
Wed Jul 26, 2017 10:45 am
To be honest, I can't see any issue with the way the strings are tied. They look very neat to me. I would be interested in hearing what people think is the issue with theses knots.
.................
Here's the pic of subject guitar. You don't see a problem?
There should be at least 2 to 3 twists on the treble strings to increase frictional surface area so it does not slip. There are no twists on his, the strings are constantly slipping as it is being played until it reaches the knot (which has not been reached yet in the pic).

Image

simonm
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Re: Repair of guitar - what needs done?

Post by simonm » Wed Jul 26, 2017 9:51 pm

SteveL123 wrote:
Wed Jul 26, 2017 4:19 pm
[
Here's the pic of subject guitar. You don't see a problem?
Not really.

I use three turns on top of the tie block myself. My teacher, however, does this kind of elegant loop as well with just a burned on knob at the end of the treble strings. I think it depends on getting the loop exactly right too. I find the triple twist/knot easier too but that doesn't mean that other methods don't work. :-)

fraim
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Re: Repair of guitar - what needs done?

Post by fraim » Wed Jul 26, 2017 11:24 pm

i use these loops on bass & trebles but i don't use those twisties that he has on the trebles. i also learned this technique from my teacher. i have no slippage on the trebles but it does take some extra time to do this type of tie. ymmv

johnparchem
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Re: Repair of guitar - what needs done?

Post by johnparchem » Thu Jul 27, 2017 3:36 pm

... She's a violinist so she tunes by ear, as do I. (She's perfect pitched ...
Guitars are never really in tune across all of the fretted positions for some with perfect pitch a guitar never sounds in tune. The fret spacing for each string would need to be modified for perfect intonation because the characteristics of the strings play a role. From what I heard guitar intonation is a way of spreading the inherent error in the guitars design as thinly or evenly as possible.

The problem with just some notes on the same string being out of tune may be an issue with the guitars resonant frequencies. I read in the Gore\Gilet Design book that a strong resonant peak near a note will tend to repel a played note away. This is some times seen tuning open notes as well where it is hard to tune to a note. I wonder if the same issue exists tuning down a semi tone.

John higgon
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Re: Repair of guitar - what needs done?

Post by John higgon » Thu Jul 27, 2017 5:09 pm

The scale length is from the edge of the nut (fretboard side) to the edge of the saddle (soundhole side). There shouldn't be much difference in that measurement from one string to another. I just make the measurement down the centreline of the fretboard. It's unusual for guitars to be significantly out of tune. I see that your guitar has a shorter-than-usual scale length, so it's worth checking that the bridge is in the right place, and it's a quick and easy check to make. However, I'd be surprised if the tuning problem is down to bridge position, frankly. It's possible that a full-size body has been married to a short neck, or vice versa, but that seems unlikely. Even so, worth a quick check.

Peskyendeavour
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Re: Repair of guitar - what needs done?

Post by Peskyendeavour » Thu Jul 27, 2017 10:19 pm

johnparchem wrote:
Thu Jul 27, 2017 3:36 pm
... She's a violinist so she tunes by ear, as do I. (She's perfect pitched ...
Guitars are never really in tune across all of the fretted positions for some with perfect pitch a guitar never sounds in tune. The fret spacing for each string would need to be modified for perfect intonation because the characteristics of the strings play a role. From what I heard guitar intonation is a way of spreading the inherent error in the guitars design as thinly or evenly as possible.

The problem with just some notes on the same string being out of tune may be an issue with the guitars resonant frequencies. I read in the Gore\Gilet Design book that a strong resonant peak near a note will tend to repel a played note away. This is some times seen tuning open notes as well where it is hard to tune to a note. I wonder if the same issue exists tuning down a semi tone.
That is very interesting...
I am not perfect pitched as she is, but I still hear some notes being more "out" than others (seem to be from random positions - but from your theory may not be so random after all ) and will have to try out tuning a semi tone down...

I will have to do it by proxy at present...

Peskyendeavour
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Re: Repair of guitar - what needs done?

Post by Peskyendeavour » Thu Jul 27, 2017 10:25 pm

John higgon wrote:
Thu Jul 27, 2017 5:09 pm
The scale length is from the edge of the nut (fretboard side) to the edge of the saddle (soundhole side). There shouldn't be much difference in that measurement from one string to another. I just make the measurement down the centreline of the fretboard. It's unusual for guitars to be significantly out of tune. I see that your guitar has a shorter-than-usual scale length, so it's worth checking that the bridge is in the right place, and it's a quick and easy check to make. However, I'd be surprised if the tuning problem is down to bridge position, frankly. It's possible that a full-size body has been married to a short neck, or vice versa, but that seems unlikely. Even so, worth a quick check.
Thanks. I was guessing down centreline, as no one until you said so. Confirms my thoughts, and compensation either side ought to be 1mm thereabouts (from above someone else said not more than 2mm end to end at saddle). :merci:

simonm
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Re: Repair of guitar - what needs done?

Post by simonm » Thu Jul 27, 2017 10:55 pm

simonm wrote:
Wed Jul 26, 2017 10:45 am
... There is a master class on you tube whether the teacher takes a guitar off the student and tunes if for him and comments while doing - "you can never get a guitar into tune, all you can do is get it less out of tune". . ...

Found it again. https://www.youtube.com/watch?v=C8BNYhLoSvo The master class is with Marcelo Kayath and at about 9.55 in this video he says something to the effect of … "forget it, a guitar can't be tuned. All you can do is get it equally out of tune" … Very funny in Brazilian. Kayath is actually avery interesting player in any case. Dropped out of playing to become a banker and recently came back to playing.

Given that the guitar owner has perfect pitch is may be a battle to find a suitable guitar. Some guitars have better intonation than others but they are in a different price category. On the other hand compared to a pro violin all expensive guitars are pretty ordinary prices or even downright cheap. Price alone will not necessarily be an indicator of better intonation.

I recall reading about someone with perfect pitch who gave up guitar because he/she could not stand the fact that the instrument was always out of tune.

Keith
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Re: Repair of guitar - what needs done?

Post by Keith » Fri Jul 28, 2017 10:04 am

scale length = nut to 12th fret x 2. see Ramirez book, posts here at Delcamp.
string length = nut to saddle
difference in lengths is compensation. most guitars have a 1-2mm compensation. many posts here at Delcamp on the subject.

sometimes it is best to start from the beginning. take off strings and toss. the strings could be stretched out, defective, etc. buy reliable set of strings--if the scale length is 630mm maybe high tension strings? make sure tuners are working correctly and lube if needed. restring using accepted tying methods. let strings settle. try it out.

rather than looking for some real bonehead mistake one should start from square one. there is a reason why most techs ask the question, is the machine plugged in, before asking additional questions. the guitar is factory made and most likely the fretboard was cut using CNC or a template so it may be safe to say all is well in that regards. that said it could have been made on a Friday at 3 p.m. when the workers were looking forward to the weekend and were not paying attention and someone used the 650mm jig for the 630mm fretboard.
be true to the one you love but have many flings with different guitars

Peskyendeavour
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Re: Repair of guitar - what needs done?

Post by Peskyendeavour » Fri Jul 28, 2017 11:17 am

simonm wrote:
Thu Jul 27, 2017 10:55 pm
simonm wrote:
Wed Jul 26, 2017 10:45 am
... There is a master class on you tube whether the teacher takes a guitar off the student and tunes if for him and comments while doing - "you can never get a guitar into tune, all you can do is get it less out of tune". . ...

Found it again. https://www.youtube.com/watch?v=C8BNYhLoSvo The master class is with Marcelo Kayath and at about 9.55 in this video he says something to the effect of … "forget it, a guitar can't be tuned. All you can do is get it equally out of tune" … Very funny in Brazilian. Kayath is actually avery interesting player in any case. Dropped out of playing to become a banker and recently came back to playing.

Given that the guitar owner has perfect pitch is may be a battle to find a suitable guitar. Some guitars have better intonation than others but they are in a different price category. On the other hand compared to a pro violin all expensive guitars are pretty ordinary prices or even downright cheap. Price alone will not necessarily be an indicator of better intonation.

I recall reading about someone with perfect pitch who gave up guitar because he/she could not stand the fact that the instrument was always out of tune.
:lol:

I asked her she says she doesn't have perfect pitch nowadays just intonation in the way that any violinist should have...

I must say I was also surprised to hear some notes more out than others and my intonation is maybe ok towards good but by no means perfect, that some notes jump out to me as out is strange as I've played a lot of different crappy guitars in different homes (I beg to play any guitar I get my hands on when I travel! :lol:) even those with cracked tops and been bashed around cheap things didn't have this particular problem...
Last edited by Peskyendeavour on Fri Jul 28, 2017 11:20 am, edited 2 times in total.

Peskyendeavour
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Re: Repair of guitar - what needs done?

Post by Peskyendeavour » Fri Jul 28, 2017 11:19 am

Keith wrote:
Fri Jul 28, 2017 10:04 am
scale length = nut to 12th fret x 2. see Ramirez book, posts here at Delcamp.
string length = nut to saddle
difference in lengths is compensation. most guitars have a 1-2mm compensation. many posts here at Delcamp on the subject.

sometimes it is best to start from the beginning. take off strings and toss. the strings could be stretched out, defective, etc. buy reliable set of strings--if the scale length is 630mm maybe high tension strings? make sure tuners are working correctly and lube if needed. restring using accepted tying methods. let strings settle. try it out.

rather than looking for some real bonehead mistake one should start from square one. there is a reason why most techs ask the question, is the machine plugged in, before asking additional questions. the guitar is factory made and most likely the fretboard was cut using CNC or a template so it may be safe to say all is well in that regards. that said it could have been made on a Friday at 3 p.m. when the workers were looking forward to the weekend and were not paying attention and someone used the 650mm jig for the 630mm fretboard.
I'm really glad that you and others all of similar opinions and what to check, as that gives comfort as to what next.
Plus... how not to throw the baby out with the bath water!

astro64
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Re: Repair of guitar - what needs done?

Post by astro64 » Fri Jul 28, 2017 4:07 pm

My advice would be to systematically map the inaccuracies across the fretboard. You may have some frets out of place. Put a good set of string on, let them settle for a few days. Bring open strings in tune. Check they hold tune. Now with a good tuner map for each fretted note on each string how far the tuning is off. Write them down on a chart. If you have one or more frets in a wrong position it will become obvious. If you see a systematic pattern of notes going sharp or flat as you move up the fretboard the saddle position is off. Note that the third string will generally be the most off because it needs more compensation than others. But the systematic patterns should still be there if either frets are in wrong place or the guitar is not properly compensated (i.e. saddle in wrong place or needs fine-adjustment to get the break point for each string correct).

Peskyendeavour
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Re: Repair of guitar - what needs done?

Post by Peskyendeavour » Fri Jul 28, 2017 8:52 pm

astro64 wrote:
Fri Jul 28, 2017 4:07 pm
My advice would be to systematically map the inaccuracies across the fretboard. You may have some frets out of place. Put a good set of string on, let them settle for a few days. Bring open strings in tune. Check they hold tune. Now with a good tuner map for each fretted note on each string how far the tuning is off. Write them down on a chart. If you have one or more frets in a wrong position it will become obvious. If you see a systematic pattern of notes going sharp or flat as you move up the fretboard the saddle position is off. Note that the third string will generally be the most off because it needs more compensation than others. But the systematic patterns should still be there if either frets are in wrong place or the guitar is not properly compensated (i.e. saddle in wrong place or needs fine-adjustment to get the break point for each string correct).
Ah I se what you mean... And it might mean after the "mapping" I might be able to change the compensation by using compensated saddle such as : tusq-acoustic-saddles - I noticed on my own guitar, which doesn't have this intonation problem and this guitar doesn't seem to have - the compensation on this particular one seems mainly the diagonal saddle.

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