Guitar Intonation, a mystery no more
When I first started messing around with guitars, I found the whole guitar intonation thing a puzzling mystery. Then the more I thought about it, it dawned on me that all we're trying to do here is cut a frequency wavelength in half. The twelfth fret of the guitar is simply one octave above, the open notes, so in order to double the frequency of a note, or move it up an octave, we have to halve the string length. So if the string from the twelfth fret back to the nut, isn't even with the string length from the twelfth fret to the saddle, then we are in fact not "intoned". Now listen, don't go checking too deeply into what I just wrote because I made it up. But the gist of it, for the most part, is correct.
Now if you have just built a guitar, or have replaced saddles or a nut, you need a place to start before you can fine tune the guitar intonation. String up the guitar and bring it into tune. Measure from the nut, the bridge side of the nut, up to the middle of the twelfth fret wire. Mark that measurement down somewhere. Now measure from the middle of the twelfth fret wire up to the low E saddle. When measuring to the saddle you want to measure to the point where the string will no longer sound on the saddle, which is where it actually touches. Make that length the same as from the inside of the nut to the twelfth fret. Now, and this isn't laser precision here, move the A string saddle back from the low E string saddle the thickness of the A string. If you're using a .038 A string, adjust the saddle back .038 inches. Do the same with the D string saddle, move it back from the A saddle equivalent to the thickness of the D string. The G string saddle should be placed parallel to the A string saddle. Now, move the B string saddle back from the G string saddle equivalent to the thickness of the B string. Lastly move the high E string saddle back from the B string saddle equivalent to the thickness of the high E string. It's important to note that after every move you should tune the guitar, always keep the guitar in tune.
Once you have the guitar intonation rough set, its time to fine tune. I highly recommend a plug in tuner for this, but use what you've got. You want to tune each string at the twelfth fret. To do this start with the low E string, or high E if you prefer. Fret the string only to the point in which it sounds. Don't press the string down to the fretboard. Lightly pick the string, and check the tuner. If the string is flat, the string is too long. Adjust the saddle back toward the nut, then re-tune and try again. Don't move the saddle screw anymore than a quarter turn at a time. Patience is key here. If the string is sharp, it's too short, move the saddle away from the nut, re-tune and check again. Do this for each string, and your done. You are now "intoned". J. Brennan.
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