Guitar Intonation

My guitar doesn't play in tune, even after I know I've tuned it correctly.
Some chords sound in tune while others don't.

After tuning an instrument to pitch you may discover that not all notes are playing in tune. Actually, some notes can be down right unbearable. Intonating an instrument adjusts each individual string length to provide the best possible tuning at each fret.

Things That Can Affect Intonation

While it is true that there is a certain amount of compromise on fretted instruments, my goal is to have the best possible intonation even when perfect intonation is somewhat elusive. Welcome to the world of the equal tempered scale!

Saddle Placement

Most electric guitars utilize adjustable saddles. Forward and backward movement of the saddle changes the strings overall length which directly effects intonation. When playing a guitar you move from one fret to the next, shortening and lengthening the string to change the note ...the same is true for intonation as we move the saddle fore and aft to provide the optimal string length.

High Action

An instrument with high action (string height) will cause the string to stretch further before contacting the fret, this stretching sharpens the note slightly. High action at the nut is particularly troublesome as chords played in the 1st to 3rd position can sound terribly out of tune.

Excessive Neck Relief

Excessive neck relief (bowing) shortens the distance between the nut and saddle and increases the string height above the frets.

Worn Saddle

Wear and tear can change the shape of the saddles crown. A badly worn saddle make change the strings contact point.

Fret Wear

Frets that are badly grooved or have flat crowns will also throw off intonation. Instead of contacting the fret dead center, the string now sits atop a worn crown which can also alter the strings length.

Frets must be leveled and re-crowned to remove the grooves or replaced if wear is excessive.

Fret Height

Instruments with very tall fret wire can play incredibly sharp if the string is fretted hard and your fingertip is bottoming out on the board. To see for yourself what affect your fretting technique has on your instrument, watch the pitch of the note on our tuner when fretting with different pressure.

Strings

Ever been tempted by those super cheap strings you find on auction sites? All strings are not created equal and I have personally encountered the problem first hand. After a super intonation tweak which had the instrument play wonderfully a client returned baffled as to why it now sounded so out of tune. The answer ...he replaced the strings with some cheapies purchased for $1.00.

Worn strings can also create tuning difficulties. If your intonation issue is a brand new problem, the instrument played in tune before and no changes have been made to the instrument you may wish to change strings first, just to rule out the easy stuff.

Pickup Height

A strong magnetic pickup sitting too close to the string will effect the intonation. I would recommend setting the pickup height to 3/32" below the bottom of the string when fretting at the last fret. Active pickups can be closer.

Sometimes clients come to me unable to intonate their instrument, or, finding that the saddles are at extreme positions without achieving proper intonation. In many cases I find the pickups far too close to the strings.

Fret Spacing

I hate to mention this as I fear far too many people will jump to this conclusion in error, but I still encounter this on occasion. Generally seen on inexpensive imported instruments and some vintage pieces with hand slotted fretboard's.

Factories are using sophisticated machines that are calibrated daily to ensure accurate fingerboard slotting.

Playing Technique

Well this isn't actually a defect, it's a playing style. Some players have a rather powerful fretting technique in which they place excessive pressure on the strings when fretting. If the instrument happens to have fairly tall frets this is more than enough to sharpen a note.

There are also some players that have a tendency to bend a string sideways when fretting, sharpening the note.

Adjusting Your Intonation

Adjusting Saddle Position

The first step to improving your guitar's intonation is to eliminate any issues that I've mentioned above which could be causing problems. It's also important to mention that adjusting intonation is the last step in a set-up. The string height and neck relief should be adjusted prior to setting intonation.

If the note at the 12th fret is ...

♯ Sharp - Move saddle further from fingerboard

♭ Flat - Move saddle closer to fingerboard

Make small adjustments to the saddles position, retune the string and check the note at the 12th fret again. Repeat until the note at the 12th is in tune.

Installing Compensated Nuts


Compensated Earvana® nut

As I have already explained, fretting the string stretches it. Length is added to the instrument's string to prevent sharpening of the note as it's played up the neck ... but, we have also lengthened the open strings.

In order to improve the tuning further some may choose to install a compensated nut. Compensation of the nut can be achieved in different ways but most have settled on a "shelf system" whereby the nut overhangs the end of the fingerboard instead of permanently shortening it.

Earvana® is one example of a prefabricated compensated nut.

The Buzz Feiten Tuning system® is another popular intonation/compensation method. Modifications are made to the nuts position/fingerboard length and intonation is adjusted according to slightly off set tunings determined by string gauge, scale length and action.

Scale Length

The scale length of an instrument can be determined by measuring from the nut end of the fingerboard to the middle of the 12th fret and doubling it. Because compensation is added to the strings length you can not arrive at the appropriate scale length by measuring from the nut to saddle.

The larger the string, the more compensation necessary.

Common Scale Lengths*

Fender Strat/Tele 25.5 "
Fender Jazzmaster 25.5"
Fender Jaguar 24"
Fender Mustang/Bronco 24"
Gibson Les Paul/SG 24.75"
Gretsch 24.6"
Guild 24.75"
PRS 25"
Ibanez 25.5"
Kramer 25.5"
Schecter 25.5"

*Some editions may vary

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