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shalomjj
09-16-2016, 05:37 PM
Is adjusting the saddle the best way to fix a slightly flat intonation or would the nut be a factor as well?

anthonyg
09-16-2016, 09:52 PM
Both the nut and the saddle are factors. Which one you adjust depends on which one is at fault;)

Which isn't always easy to know. If its open position notes that are flat or sharp then its good to adjust the nut. If the intonation is flat or sharp at the 12th fret then adjusting the saddle is a good place to look but both are always a factor.

I start by measuring up the instrument to see if I can notice a variation in the measurements that may be the cause.

Before I get too long winded. How good are you with measuring things and do you have a good steel rule that's long enough?

Anthony

shalomjj
09-16-2016, 11:53 PM
Thanks Anthony! I have my engineers ruler and am glad to hear some advice. I have set up ukes before and usually the problem is it being too sharp. I measured the action at saddle and it is 2mm so raising it might help. But, in comparing my tenor that is flat with another use in perfect intonation, I noticed the nut spacing to the first fret is a bit shorter. I don,t know if there is a way one can compensate the nut? Please share your method of setting up a uke :iwant:

anthonyg
09-17-2016, 02:07 AM
OK, String height is a small factor, what's a bigger factor is the distance of the nut and saddle from the centre of the 12th fret.

First, what is the instruments, Nominal scale length?

ACTUAL scale length is the nominal scale length + compensation. This can be broken down further to be the distance from inside the nut to the centre of the 12th fret x 2 + compensation.

The centre of the 12th fret should in theory be exactly in the middle of the string length, however this theoretical scale length is dependant on theoretically perfect strings. Since strings aren't "perfect", compensation at the saddle is introduced to correct the tuning (intonation) of the instrument.

OK, if an instrument is built to theory, then the intonation (tuning) will go sharp. To correct this the saddle is placed further away from the centre of the 12th than theory dictates. If the saddle is placed TOO far away, then the intonation goes flat.

That's the simple answer.

Now this "simple" position is complicated because the placement of the nut is a factor just as the placement of the saddle is a factor.
So, move the saddle away from the 12th fret, you flatten the intonation, move the saddle towards the 12th fret, you sharpen the intonation.

At the nut, move the nut away from the 12th fret, you sharpen the intonation, move the nut towards the 12th fret, you flatten the intonation.

So, what's the nominal scale length of the instrument? Measure both ways from the centre of the 12th fret. Are the contact points where they are supposed to be? Are they closer, are they further away?

Anthony

shalomjj
09-17-2016, 05:42 AM
Thanks Anthony. I measured and used the Stewart Mac fret calculator. The distance is too small on the first fret. I found a bone nut that has a slanted edge and may try to reverse this to make a compensated nut which might just do the trick. Only $3 for the part plus a new saddle.

anthonyg
09-17-2016, 06:21 AM
Thanks Anthony. I measured and used the Stewart Mac fret calculator. The distance is too small on the first fret. I found a bone nut that has a slanted edge and may try to reverse this to make a compensated nut which might just do the trick. Only $3 for the part plus a new saddle.

I'm glad I helped. Its always a balance between nut placement and saddle placement. I find that having the nut just a fraction closer (which flattens the intonation) to be helpful as its common for the intonation in the open position to go sharp, but we are talking about very small adjustments.

I've just about corrected the intonation on ukuleles that didn't have any saddle compensation by introducing the compensation at the nut.

Also, since the saddle is too close, its possible to take a dremel tool to the nut and take the contact point back (slowly) at each string until the strings are right individually. You will find that the outer two strings will usually need to be closer to the 12th fret than the centre two strings need to be.

Anthony