Variability of intonation between Strings

I've been playing a few years now and do a few bits of basic Uke repair and maintenance: replacing strings, nut and saddle set-up.

Something that I've noticed, but not recorded or quantified, is a variability of intonation between string brands and between the same brand of String fitted to a Uke. I have a Kala KA-P fitted with Martin 600's that's near perfect intonation up and down the fretboard - cut the nut, adjusted the saddle and fitted the strings myself. I also have a virtually identical Lanikai LU-21 P that is fitted with Aquila strings, it's second hand and old but must have been played a lot (loved?) by someone as it's virtually mark free and the old strings were heavily ridged underneath. Again I cut the nut to drop the string height (1.2 to now 0.5mm at the first fret), checked the saddle height and replaced the strings with Aquilas. The Lanikai sounds just fine in use (to my ear and when making chords on frets near to the nut) and is destined to become my travel Uke.

So I now have two 'virtually identical' Ukes however they aren't identical in intonation. Some strings on the Lanikai have better intonation (less sharp) than their neighbours; whilst none are perfect the A string is vitually so - the A is typically in tune at every fret including the 12th fret but the C and E only stray in tune (sometimes) 'till the the 6th and the G (typically) to the 3rd. Different strings on any randomly chosen fret are sharp by differing amounts and the same string can vary in being in tune and degree of sharpness along its length.

The nut seems correct. I've done several nuts now and worked carefully, also setting the tuning (up a semitone) off of the first fret instead of the nut doesn't appreciably alter anything either [EDIT. Tuning off of the second fret instead (a whole tone up) does put some of the strings fractionally more in tune for the chords normally used for strumming, might take to doing that on my other Ukes too]. The saddle gives a 3.00 mm string height off of the 12th fret so is about right, putting a coin on top of the fret (depress the string less and fret off of the edge of the coin) doesn't change the sharpness much. The saddle position has been checked too and is where one would expect it to be (the 12th fret appears to be midway between the nut and saddle).

I'm left wondering whether some strings just play more in tune than others. What do you think and what have you observed on your own instruments?

Spacing between frets not consistent between the two ukes?

uke1950 said:

Spacing between frets not consistent between the two ukes?

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Well I had wondered about that too and held them side by side looking for anything obvious. But I'd be very surprised if any of the frets were in the wrong place and the LU21's A string scale being virtually perfect supports a correct build too. If the G string had been similar to the A then I'd have wondered about saddle position and then bridge compensation - though that's not usually an issue on Sopranos. Thanks for the suggestion though.

Yep. Itʻs a moving target. Thereʻs no such thing as perfect intonation on a uke. At a certain point you have to tune with your fingers as you play to get any more precise.

Flurocarbon strings tend to intonate better than anything else. Put some on the Lanikai and I bet most of your intonation "problems" will go away.

Hippie Guy said:

Yep. Itʻs a moving target. Thereʻs no such thing as perfect intonation on a uke. At a certain point you have to tune with your fingers as you play to get any more precise.

Flurocarbon strings tend to intonate better than anything else. Put some on the Lanikai and I bet most of your intonation "problems" will go away.

Click to expand...

Thank you for your post, it's a help, it's appreciated and it's also nice to have a comment from someone so professionally involved with Ukuleles too.

I will adopt the simple way forward, at some point I'll put Fluorocarbon Strings onto the Lanikai.

At the moment I have tuned up the Uke off of the second fret (obviously up a tone there); all the strings are in tune from the second fret right up to and including the seventh fret - basically everywhere it needs to be in tune for strumming - so that should be OK for playing just chords at the Uke Club for a while.

Out of interest I checked the Kala's intonation this morning, fluorocarbons are already on that Uke. Each of the Kala's strings were in tune at the nut, at the 12th fret and at virtually every fret in-between the two too.

If the Lanikai intonates ok with a capo on the second fret, then it's likely that the action at the nut is too high. This will throw off all the fretted notes up to the 12th, even if the 12th is accurate (the errors should decrease as you get closer to the 12th).

Test the nut action by fretting between the second and third frets and then checking the string height over the first fret. You're looking for the string *barely* to clear the first fret - easiest to tell by gently tapping/pushing the string with your finger over the first fret, so you can feel how far it moves down before fret contact.

I don't find Aquila Nylguts to intonate worse than any other string.

In all my string testing, regardless of brand or string material, I've observed that the closer the string gages are to each other, the better they intonate 'as a set' up the neck...

i.e., with a perfect scale length and perfectly parallel saddle and nut, without any compensation to the nut, strings with a narrower spectrum of diameters across all four, seem to all go sharp THE SAME AMOUNT, as you go up the neck, so 'relative intonation' to each other is improved compared to strings that a thinnest on the A and fat on the C, having said that, Martin fluoro strings seem to be an anomaly in this regard with the A being a 0.0191" or 0.0216" in the M600 and M620 sets respectively, but both having the C string be 0.034" (thickest of ANY fluoro set available).

One example of strings with closer gages are the re-entrant Oasis sets:

the BRIGHT set is 0.021", 0.026", 0.029" & 0.023"
the WARM set is 0.023", 0.026", 0.029" & 0.025"

The WARM set is very close in gages, if not in fact the same as the Worth CT & BT, and Living Water tenor re-entrant sets, however each of these sets may in fact be source from different formulae of fluorocarbon polymers (ahem, Seaguars 'Blue Label' vs 'Premium' lines, etc)...