You're up nice and early Jack...bacon and eggs?
I'm about to ZZZZZZ.
A cut and paste from my notes:
INTONATION.
Before actual adjustment of the intonation, the string saddles can be placed in their approx positions.
With a tape measure, measure the distance from the inside of the string nut (at the top of the neck on the fret board side) to the centre of the 12th fret. Double this figure to give you the scale length of the Bass. If the initial measurement is 17 inches, then the scale length is 34 inches (2x17 inches).
Position the G string saddle to the scale length of the Bass ie it should be exactly 34 inches measured from inside the nut to top centre of the saddle.
Position the D string saddle back from the G saddle (towards the end of the Bass) at a distance equal to the gauge of the D string…eg if the D gauge is .065 inches, then move it back from the G saddle .065 inches. If the A string gauge is .085 inches then move it back from the D saddle .085 inches. If the E gauge is .105 inches then move it back from the A saddle .105 inches.
If fitting new strings then, after tuning them to pitch on the tuner, press down on each string on the inside of the saddle (on the pickup side) so they make good contact with the saddle (see article on how to fit new strings).
The needle on some electronic tuners fluctuates when tuning. Tip: only use the neck pickup & turn off the others, if any. Roll back the tone controls and pluck the string close to the heel of the neck. A plectrum may help instead of plucking with the finger. The idea behind this is to reduce the harmonics which confuse the tuner and to emphasise the fundamental note.
With each string in turn, play the strings’ 12th fret harmonic and tune it to pitch on the tuner. A harmonic is played by touching the string OVER the 12th fret with your finger and plucking it without actually fretting the string. The string will give a ringing sound. This is the strings’ natural octave overtone and should be in tune to the open string. If not, the string is faulty. Now, play the 12thfretted note on the same string. Both should be in equal tune, on the tuner, if the string is intonated correctly. If the fretted note is either sharp or flat then adjust the strings’ length accordingly at the bridge. If sharp, the string is too short…move the string saddle back towards the end of the Bass. If flat, the string is too long...move the string saddle towards the top (neck) of the Bass. Adjust the saddle screw a ¼ turn at a time. After each turn, retune the strings harmonic on the tuner BEFORE going back to check the fretted note. Keep repeating until the fretted 12th note and the 12th fret harmonic both read in tune with each other.
Don’t proceed on the basis that it’s the harmonic that has to be adjusted. It’s the 12th fretted note that has to be adjusted.
A tuner’s accuracy can be rather broad. For true intonation accuracy, now go to the 19th fret of the string being adjusted and make sure it reads in tune with the tuner eg. the 19th fretted note on the E string is B. After checking the 19th note, go back and check the 12th as they interact on each other. Don’t forget…retune the harmonic to pitch after each adjustment to the string, before rechecking the 12th fretted note.
After adjusting intonation, go back and check the string heights.
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