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Problem when changing tunings

Q: Hi there from Scotland!!

I've just had my 23-year-old Martin MC-28 refretted, new nut and set up by the authorised repairer. I use Martin Phosphor Bronze light gauge strings and it sounds brilliant. However, when I detune (especially in DADGAD tuning), the B string sounds duff!! The other strings are fine. Should I put a kind of shim either under the nut (which is floating) or under the saddle, or should I leave it alone? The repairer told me that all sorts of problems arise when tuning down, especially with light strings. My mate's guitars sound fine with extra lights, so what do you think?

Shall I leave it well alone, or shim it? Should I shim it at the nut or saddle? What could I shim it with?

Thanks for your time.

A: By "duff" I presume you mean that it's buzzing. Rattling against a fret or two. You have roughly 25 pounds of tension on each of your strings.a total of 160 pounds of string tension with light gauge strings (look on the package of a set of D'Addario EJ-16s for exact figures). When you lower the E, B, and high E a whole step each, you have removed at least 10 pounds of pull. Your neck is not rigid. It is planed with exactly enough bow back so that the recommended strings and tuning will pull it perfectly straight. If your MC-28 had been made after 1983 all you would need to do would be loosen the truss rod a tad. Unfortunately you have no truss rod so a simple neck adjustment involves pulling the frets, planing the fingerboard and driving new frets.

But, you also said that the B is the only string that buzzes when you go to DADGAD. So you need to check to see if the string buzzes against the first fret. Then put your finger on the first fret. If the string does not buzz against the second fret, your nut is too low. The nut height only controls whether or not the string buzzes on the first fret. If it buzzes anywhere else it is not a problem with the nut. If the B slot in the nut is too low it can be filled with bone dust and super glue and refiled. This works perfectly with bone nuts. Your original nut was made of Micarda and the super glue doesn't always stick. Hopefully your new nut is bone.

If your string is buzzing on one or two higher frets you need your frets leveled. If it buzzes evenly all the way up you can just raise the saddle. You need a solid connection between the bottom of the saddle and the bottom of the saddle slot. If you try to shim one end you will leave a gap. You can put a hard wood shim all the way across and then reshape the top on the saddle so that only the B is raised. Remember that the 12th fret is the halfway point of an equilateral triangle with it's apex at the nut and it's base defined by the amount you are going to change the saddle height. If you want the string to move 1MM closer to the 12th fret, you must cut 2MM off the saddle. If you want to raise the B string 1/32" at the 12th fret the saddle must go up 1/16".

I don't know what you mean by a floating nut. The saddle, in the bridge is not glued down. It's held in place by string down pressure. Nuts are always glued in. Is the nut/saddle terminology switched in Scotland?

I'm sure that if you took your guitar back to your luthier and asked him to adjust the guitar for DADGAD he would be pleased to do it. But then, when you tune back up to standard, the action will be higher than perfect. The fact that only your B string buzzes may mean that the others are already higher than necessary. I would give your luthier a second chance on this guitar. It often takes two tries to get an action right. Sometimes the tension has been changed so much that it takes the guitar a few weeks to get used to the new load. Sometimes the luthier doesn't have a clear idea of your style and gives you a generic action. When you say "no, higher/lower" he will nail it on the second try.

You mentioned ultra light strings. They are just wrong. You must use them on very old, very small guitars, but they don't have the mass to move the top of a modern guitar. Have your friend try moving up to light gauge. If they hurt his fingers, he needs an action set.

If by "Duff" you mean that the string is weak and floppy sounding? The pitch of a string is defined by the length of the string, the mass of the string and the tension on the string. The pitch is changed by varying any of these three factors. You can raise the pitch by making the string thinner, tighter or shorter. A string must be pulled to about 80% of breaking tension to make it "sing". To make it act more like a fluid than like a rod. A light gauge B string is a .016. They sound great pulled up to B. Tuned down to A, a .017 might sound better. Some serious DADGADers use, from the top: .013, .017, .024, .034, .044, and .058. Some have a different guitar for every tuning they use. If you must use the same guitar for lots of tunings have your luthier adjust the action for the tuning with the lowest tension. When you go to the higher tension tunings the guitar will be harder to play.