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I have a problem with intonation adjustment on my g-string on my Epiphone Les Paul. It's correct now but the bridge saddle cannot be adjusted any farther in range.

I need to change strings but I don't know what strings I have now and worry that I might have problems with intonation if I buy the wrong strings.

So how does string gauge affect intonation? Do I need to buy thicker or thinner strings?

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This question refers to intonation.The 'octave adjustment ' is how this is checked.Yes, other gauge strings will cause the saddle to need adjustment, and possibly the truss rod may need the same, too. To check string 'width' use a micrometer in thous (thousandths of an inch). The question, whilst poorly phrased, is hardly ambiguous. –  Tim Jun 2 '13 at 19:06
    
Thanks guys - I have edited and reopened (but please check I haven't broken the meaning of the question) –  Dr Mayhem Jun 2 '13 at 19:28
    
Welcome to Musical Practice & Performance, Luke! Dr Mayhem and I had to edit your question extensively because you seem to be a beginner who does not understand the correct terminology in describing parts of the guitar. I hope that you can still recognize your question after we have rewritten it. –  Wheat Williams Jun 3 '13 at 1:08

4 Answers 4

up vote 11 down vote accepted

You have asked two questions.

First

"What is the measurement of the G-string that you should use on your Epiphone Les Paul guitar?"

The correct technical term for what you call the "width" or "thickness" or "diameter" of the string is its gauge.

Take your guitar to a qualified guitar technician or luthier, or at least to your local music store, and have them examine the guitar. They can use a measuring device to tell you the exact gauge of strings that are on the guitar, or they can simply estimate it by looking at the strings. They can recommend what set of six strings you should purchase to replace the strings that are on your guitar now. They can also sell you individual strings if you don't need to replace all six.

Epiphone Les Pauls usually ship from the factory with a "set of 10s", which is to say a set of strings where the highest string is 0.010 inches in diameter, and the other five strings make up a matched set of gauges that work well with the 0.010-inch string.

Different sets of strings sold by different manufacturers will vary in the gauge of each individual string, but typically an Epiphone Les Paul would come from the factory with a G-string that is unwound and is 0.017 inches in diameter.

For example, below, I have provided a screen shot of a chart showing the standard string gauge specifications in a set of Gibson Brite Wires nickel-plated steel round-wound strings. This is a popular set of string gauges for a Les Paul-style guitar.

enter image description here

Second

you asked "So how does string gauge affect intonation?"

It is not so much a question of the string gauge affecting the intonation. Rather, it is that a guitar requires several different types of adjustment in calibration to work correctly if you decide that you would rather play with heavier strings or lighter strings. Adjusting the position of the bridge saddles is only one of these types of calibration.

Doing this requires a professional setup (a topic I have written about many times on this site, and something that beginning guitarists seem not to be aware of). If you want to use heavier or lighter-gauge strings on your guitar, you need to take it to a professional guitar technician and pay them (usually between $50 and $150 in the USA, in my experience) to change the calibration of several parts of the guitar, interactively, to work correctly with the heavier or lighter strings to produce proper intonation, to make sure all notes sound clearly, and to make the guitar easy to play (so that the height of the strings from the fingerboard and frets is neither too high nor too low). Adjustments and calibrations need to be made to the nut, the neck's truss rod, to the calibration and position of several mechanical parts in the bridge (particularly if it is a tremolo bridge like a Fender or Floyd Rose), and in extreme cases the frets or the fingerboard may need to be modified.

In short, you are correct that it is simpler to keep the same gauge of strings that are already on the guitar. Going to heavier or lighter-gauge strings would probably throw the guitar out of its proper calibration to the extent that it would be wise to pay for a professional setup. However, be advised that from time to time your guitar could benefit from professional maintenance and a setup even if you keep using new sets of the same gauge of strings. This is because, like any precision mechanical device, guitars and their necks can go out-of-calibration and change their shape or angle due to changes in humidity or temperature or the wear and tear of your playing the instrument over the years.

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There's not a recommended gauge per guitar, it's all up to the player. On a floating bridge you have balance issues, but the ELP is a fixed bridge, so it's really down to tone vs playability. Thick gagues sound fuller, but are harder to play on at speed. –  Alexander Troup Mar 13 at 9:20

On some Gibsons/Epiphones, the saddles are triangular in section, as in a right-angled triangle. This means that it is possible to take off the saddle and turn it through 180 degrees, and the point of contact for the string will move back or forwards enough to get the extra adjustment for intonation you require.

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If your out-of-range saddle is under plain string, you will probably be okay if you change string gauge (without changing action). If the out-of-range saddle is under a wound string, then it could go either way.

Ideally speaking, gauge does not affect the intonation of unwound strings which are made of the same material and tuned to the same note in the same string position of the same guitar. This is because although there is more tension in a thicker string, the stress is the same. A string which has twice the cross area has twice the mass, and so it needs twice the tension to get to the same pitch. The result is that the stress (force per unit cross-sectional area) is the same. Stress is measured in the same units as pressure: Pascals.

If the action is also the same, then it means that the elongation of the two strings is also the same due to the same geometry of the situation: when we fret either one at the same fret, we are elongating it by the same amount. Fractional elongation of a material is called strain. We are adding the same amount of strain to the thicker or thinner string, and the change in stress depends only on the strain and the material's elastic modulus.

Intuitively, if the string has, say, twice the cross-sectional area, then it's somewhat as if you had two strings of the original size in parallel. Now there are going to be factors that creep in that will make some small difference, like neck relief changing under stress, the fact that the string is not an ideal string but actually a long skinny bar (and so a string with twice the area perhaps does not require exactly twice the tension to get to the same pitch), and material differences.

Material makes a difference because different materials require more or less tension to stretch the same amount (that elastic modulus thing again). For instance nylon strings for classical guitars have a low elastic modulus. They strain easily under low stress and so their pitch does not change much when they are fretted. For the same reason they do not respond to string bending very well.

If the unwound string is made of two materials (like via plating applied to a core) that also creates the possibility that the intonation will change, since their ratio will probably be different in the different diameter.

Things are far less clear with the wound strings. The winding contributes to mass, thereby lowering pitch, but does not contribute much to the string tension, which is carried almost entirely by the core. Intonation almost certainly will change with a change of unwound gauge, or from change from plain to wound or vice versa because the thickness of the core as well as the amount of mass added from windings are changing simultaneously, and so the stress in the plain core will certainly be different at pitch, even if it is exactly the same material. Since the proportionality of mass and tension is not maintained, the intonation could go either way.

So if you're changing gauges without changing action, and keeping three plain strings plain, then you can expect not to have to do much, if anything, in regard to the three plain strings if they are the same "series" from the same manufacturer (same material). The saddles for the wound ones will likely need more adjustment.

I have found this to be approximately the case in actual experience, when changing among .009, .010 and .011. The theory, of course, goes out the window if you adjust action and/or neck relief.

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Brilliant answer. It helped me understand some points, but I've played for 50+ years. It goes way beyond what I think the O.P. needed, but there again,loads (hopefully) of others will read this and be enlightened.I'm really glad the question was reinstated.What mileage is there in frightening newcomers away from this very useful (and thought-provoking) site? –  Tim Jun 3 '13 at 11:25
    
@Tim Thanks. I had most of this stuff figured out by the time I was 15. At around that time, the burning question I had was: how much harder is it to actually press/pend heavier gauge strings, in terms of pressure on the skin rather than absolute force? It's worse than linear because the contact area grows with the diameter, but the string tension (hence force required) grows with diameter squared. Thicker strings concentrate more force per area of your finger's skin. That's probably why even a small increase can be so uncomfortable: rising pressure above/beyond the extra force. –  Kaz Jun 3 '13 at 21:18
    
That's why on most of my guitars I use 008/010/012 strings for top three. Some say I lose tone, but I'm past caring !! –  Tim Jun 3 '13 at 21:21
    
@Tim If thin strings are bad, then burn all the classical fiddle records. :) The tone of light strings is just, different. There is a sound you can get from a .008 string that you won't get from a .011 at the same pitch (and vice versa). You still have a .011 in that light set; it's just, ahem, down-tuned by a perfect 4th from E to B! –  Kaz Jun 3 '13 at 21:33
    
This is a most interesting post. I'd like to add that (from the point of view of explaining one of the reasons why longer pianos have a better bass tone) the thicker the string is, the more off-pitch (skewed to high) the overtones are. (Guitars are probably too short for this to be a factor.) The reason is that the overtones derive from simultaneous vibration of the string in fractions of its length. For example, the string vibrates in halves, each half going in opposite directions, which produces an overtone an octave higher than the fundamental. (more) –  BobRodes Mar 12 at 18:38

Epiphones electrics have a known problem with intonation on the G string.

I am an acoustic player mostly, and it drives me up the friggin' wall. Most electric guitar players cannot hear it because they play with high gain, but if you finger pick, you can hear it.

The problem is: the G string intonates fine at open and 12th fret. But play an "A" at the 2nd fret and it is off- noticeably.

So, my solution was to replace the unwound G string with a wound G string. Problem solved! As a mainly acoustic player, this does not bother me in the least. YMMV.

I don't know the technical reasons behind this fix. I just know it works for me - and it's simple.

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If the wound string is denser, i.e. heavier, the speaking length would be different from that of the plain string. Instead of changing the intonation, you've put the appropriate gauge of string on for the saddle position. –  Tim Mar 13 at 7:59

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