Setting Intonation for Electric Guitars

Intonation need not be some mysterious act of your guitar tech. True, it does help to have a good strobe costing several hundred dollars but if you are touring and do not have access to a good technician, you can set the intonation quiet close using a good low-cost personal electronic tuner. It probably won’t be exact, but it may be better than what you have, or as Lemony Snicket might say, “or maybe not”, depending upon your skill and understanding of what to do. It usually helps to know what causes a problem when correcting it, so I’ll begin by explaining the cause, and then proceed with how to correct it.

Intonation Problems: The Causes
Intonation problems are noticed when a fretted instrument has been correctly tuned but as you play, it still sounds out of tune. Several things can cause this “out of tune” problem, the main one of course being that the intonation has not been set correctly. If it has been set up by a good technician and has not been changed by someone tinkering around with it, the following problems are the first things to suspect:

Bad or Old Strings
You cannot expect any fretted instrument to note correctly with poor strings. There have been times I have had to change a string that was poorly intonated as many as three times before finding a good string, and that’s using new ones. It’s not common, but it has happened. Anytime a string shows discoloration (tarnish, rust, etc.), and you are experiencing tuning problems, you should install a new set. I don’t like setting the intonation on a guitar or any other fretted instrument if the strings are over a week old and I much prefer installing a new set when doing so. If you set the intonation using an old set of strings, the instrument will be incorrectly set when you put on new ones.

The nut is bad
I don’t see this problem as often, but it could save you some head aches by checking the nut for chipping under the string, the nut coming loose or the nut was incorrectly notched for the strings to begin with. The bottom of string slots should have a slight angle downwards towards the headstock. I generally cut them at the headstock angle if it has one. If not, I angle it towards the bottom of the string post where the last winding of the string is before going to the nut, or the bottom side of the string tree if it has one.

Ball end reinforcement winding too long
I have experienced strings with this problem, and sometimes it’s caused by bad design of the saddle to string stop length. When either of these problems occur, part of the string ball re-enforcement windings will rest on top of the saddle. If it’s a string problem, you have no choice but to change to a different brand of strings, assuming that the brand that caused the problem are all the same.

Why fretted instruments need intonation adjustments

Strings for electric guitars are composed of various metals, and any time you stretch this thin wire, it will increase the tension of the string and raise its pitch. Thus, when you note a string at any point on the fretboard, you are in effect stretching the string from its natural rest state when bending it down to the fret. This bending/stretching of the string is what causes it to go sharp. The 12th fret of a guitar is commonly recognized as the halfway point between the nut and the saddles. Slightly touching the string at this point and plucking the string creates a harmonic of the string at twice the pitch of the string played open, or not noted. If we could note the string at this 12th fret without flexing or bending the string, intonation would not be needed. If we could raise the fret to the string instead of bending the string down to the fret, intonation would be a moot point. But since we can’t, it is. To make corrections for this stretching of the string, and in effect raising the pitch, we must compensate for it in some way. You could compensate for it by the spacing of the frets, but this only works if you were to use the same string gauge made by the same manufacture with strict standards to the alloys and processes used. This is not a choice that musicians are willing to stick to as you never know what brand/gauge of string the customer desires for playability and sound. The easiest way to compensate for the problem and give musicians a free choice of strings is to increase the length of the string while leaving everything else as it is, assuming everything else is correct to begin with. Correctly increasing the string length over twice the length from the nut to the twelfth fret will cause the string to note correctly by compensating for the raising of pitch when the string is pressed down to the fret.

How to set intonation

Most important is to begin with a new set of strings, pre-stretching them, or allow a day or two for them to stretch in naturally. In the shop, I always pre-stretch strings as it is much quicker than waiting for them to stretch on their own. Use a good quality tuner that will hold it’s needle position for at least a few seconds before moving. You will have a hard time of it trying to work with a tuner that exhibits quick or erratical needle movement. I have found Sabine tuners to work well when I do not have access to a good strobe tuner.

Tune the guitar to standard A=440 pitch using your tuner. Check them more than once as tuning a string and then tuning another string can cause the first string to go out of tune again. When the guitar has been tuned as good as possible, lightly touch the high “E” string, “high” meaning the highest in pitch or tone (the one on the bottom), directly above the 12th fret. Pluck the string and remove your finger that’s on the string. If you tuned correctly, the tuner needle should show the string tuned correctly to the note of “E”. If not, retune till it is shown correct on your tuner. After it is correctly tuned using the harmonic at the 12th fret, note the string at the same 12th fret and pluck the string again. Do not push the string down excessively hard as this will stretch the string more than it would be stretched in normal playing. String instruments should only be noted hard enough to make good contact with the frets to prevent string/fret buzz and no more. This is especially important when playing electric guitars that almost always use light guage strings which are easy to bend.

If your electronic tuner shows the string to be correctly tuned, not flat or sharp, then the intonation is correct, or at least within normal hearing error. If it is not, you will need to use the correct screwdriver to fit the saddle intonation screw to correct it. The saddle intonation screw is normally the long screw which comes into the back of the saddle and will usually have a spring on it to keep tension on the saddle, preventing it from moving inadvertently.

If your tuner shows the string noting too sharp, the overall string length is too short. Turn the intonation screw clockwise while keeping pressure against the screw head. Applying pressure to the screw while adjusting it should keep the screw itself from backing out from the back side of the bridge plate. Turn it about two complete turns and retune the string. Recheck the intonation at the twelfth fret again. If it’s still sharp, repeat until there is no difference shown on the tuner with the string noted or played open (or at the 12th fret harmonic). If you should adjust the saddle too far, the string length will be too long and will show up as being flat when noted at the 12th fret. If this is the case, you must turn the adjusting screw counter-clockwise to shorten the string length until correct.

If the string showed flat to begin with, the string length would have been too long and must be shortened using the same method in reverse as to when it was sharp, or too short.

Repeat the process for each string until they have all been set correctly. Once a string has been set correctly, it is generally not necessary to check them again. I would recommend using a screwdriver long enough so that the handle will not be over the body of the instrument. I have seen some deep indentations on the top of guitars by someone using too short a screwdriver. Try to use a good quality screwdriver correct for the screw size. Too small and you’ll damage the head of the screw and not be able to adjust it. Too large and it won’t fit.

It is advisable to stay with the same gauge strings that was on the guitar when it was set up. If you change gauges, you might get by with it, and again you might not.

This should be information enough to set the intonation on most guitars. Floyd rose type tremolo systems are a bit different but the principal is the same. Just remember, considering all things, if it’s sharp, it’s too short. If it’s flat, it’s too long!

Later…

Connor

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