High end tuners will tune better, hold tune better, sound better and weigh less. I use Waverly tuners. Ivoroid or Ebony buttons.
Of all the low end tuning machines Grover Rotomatics would be my last choice in tuners. They're big, bulky, heavy, the tuner posts stick up high above the peghead; the housings are large and extend off the backside of the peghead. All of this creates a misbalance in the guitar in the neck-weight compared to the body weight. The heavier the tuning machine the less sound gets down the neck back to the guitar. In effect, the weight of the tuning machines absorb string energy.
Procedures and Fit
When I replace Grover Rotomatics with Waverly tuners I use a conversion bushing 3/8 in the peghead and a wooden plug in the backside of the peghead. Depending upon what tone the individual wants I'll use ebony as a plug for bass tone, mahogany for the existing tone and pernambuco for a brighter, ringy tone. The customer has three choices of wood to plug the peghead holes with. If no wooden plug is used there is a 3/8" hole in the back of the peghead leaving a large hole or void dead air pocket.
Tuner Post Height and Downpressure
I like to shorten the tuner posts on Waverly's along with the conversion bushing or grommet. This increases downpressure on the nut. This makes the overall sound of the guitar stronger.
My findings have been that the biggest jumbo frets give the biggest sound. The smaller frets transmit the smallest amount of sound, ie. string transmit to the fingerboard. My favorite fret size is the 6000 Jim Dunlop series fret which is what Stevie Ray Vaughan used on his guitars. This is actually a bass fret. I first used these in 1986.
Changing standard Martin frets and going to the 6000 series is a remarkable gain in tone, volume, and playability of the guitar. In using the 6000 series fret or the 6105, the tips of your fingers never touch the fingerboard, only the strings, because you're 55 thousandths or 60 thousandths off the fret board. So you have more initial pop from each note and each cord so the sustain is greater and longer as well and bending is a breeze. Also it takes less effort on your fretting hand to hold the notes down than it does on a smaller fret.
Setup with fret change
After installing jumbo frets most guitars will need a taller nut and a taller saddle. So you gain down pressure on both ends of the guitar. which also results in more volume and more string energy transmit.
Guitars with long, wide, thick pegheads have more weight and mass to move than necessary for optimum sound.
To quote Norman Blake "A slothead peghead is superior to a solid peghead because of the open tuner mechanisms." I agree entirely with that and would also add that you have more downpressure on the nut with a slothead than with a solid peghead.
Set for Ideal
Why is Neck Angle wrong?
When your action is too high, and your saddle is too low, in which case like most old Martins, you have sky high action and a toothpick saddle and the guitar is incapable of playing in tune. At this time the guitar needs a neck reset. After a proper neckset you should have good action and a considerably taller saddle. Your strings will have good down-pressure on the saddle and your playability is better than ever.
String spacing and string height in open position. Most factory nuts the strings are deep sunk in and pinched in the nut slots. However, the properly finished nut, when the string height and spacing are achieved, should then be top filed and back filed to where the strings are close to half submerged and half exposed. Then the guitar will have a wide-open sound as far as the nut is concerned.
The nut not only transmits the sound but also filters the sound. Therefore, depending upon what material is chosen for the nut, you can tune in or tune out undesirable tones. For instance, a dull muddy toned guitar would benefit from fossil ivory which will brighten the tone; a bright-tone guitar should only have cow bone or maybe even ebony for a nut.
There once was a time that I used fossil Ivory (FI) exclusively on every guitar. Since then I've reached the conclusion that brighter is not better. Cowbone is harder gives a broad hardhitting sound and is much less expensive than FI. An Ebony nut produces a broad bass/woody tone. Case in point: Norman Blake's 1934 D-18 used on the Whiskey Before Breakfast recording. All of my own mahogany guitars have an ebony nut.
Compensating for String Wear
In the making of a replacement nut for a guitar the strings should be set up high enough to allow for some settling in. A guitar with a nut height close to Les Paul action will clear fine on Monday but by Friday will be buzzing on the first fret.
Scalloping the nut is done in between the strings which gives a hotter, brighter tone. Early on this was a common procedure that I used to increase sound and volume However, I have since concluded that after scalloping in between the strings the strings can settle into the string notches more easily and the action gets closer to the first fret, much faster because the string slot actually expands with no mass on either side, so I rarely scallop nuts anymore.
A big heavy bridge greatly reduces the sound of the guitar. Case in point: I'm currently doing a setup on a 1970 D-18. The bridge in the middle between the D and G strings measures 400 thousandths thick. This is easily 50 to 70 thousandths of an inch too thick, which is like having a mute on a guitar. Two Martin Bridges of equal size and shape, one of ebony, one of brazilian rosewood. The one of brazilian rosewood will be 1/4 ounce less weight than the one made of ebony.
Bridge Plate: Material
I like Black Locust or Pernambuco. They both are rigid materials and have a good tap tone.
Generally I use the old Martin herringbone design and shape if the guitar does not have a problem top and/or need a bigger bridge plate for stability.
Micarta is layers of paper with epoxy glue compressed. Produces a dull tubby tone.
Cow bone is what I use the most. It is hard, wears for a long time, gives a strong bass hard hitting sound.
Many people make the mistake when they hear the term fossil ivory that the ivory is fossilized. If the ivory were in fact fossilized it would be turned to stone. Whereas the term Fossil Ivory (FI) is a term used by fish and game to ensure that ivory is at least 100 years old or more and that no mammals have been recently killed to obtain raw ivory.
There are many types of fossil ivory. Walrus, Mammoth, Mastadon.
Fossil Ivory and the Sound
Mammoth Ivory is a soft material that gives a somewhat lower bass frequency and is easy to obtain.
Walrus fossil ivory is harder a better material and gives a very bright tone. Once there was a time I only used fossil walrus ivory for setups. But I find it too bright for most applications. On a tubby tone or dull tone guitar it may still be a good material. Fossil Ivory Bridge Pins are heavier than any kind of wood bridge pin which is why I rarely use fossil ivory bridge pins myself. My own guitars all have Pernumbucal or Ebony bridge-pins; I want to accentuate a woody tone, not a bright stringy tone.
Scalloped Braces or Straight?
A scalloped braced guitar will be looser and have a broader, bigger sound and response level than a straight braced guitar.
However, if you live below the Mason Dixon line like I do, I've seen many scalloped braced guitars with very humpy tops because the guitar was played in high heat or high humidity. What is ideal is to have a scallop braced guitar to play at home or indoors and a straight brace guitar that is more stable to play in undesirable conditions.
Front-Plate / Top-Bar
In many cases I will remove the popsicle plate from under the fingerboard to allow the entire top of the guitar to move like the old Martins from the '30s.
I add side reinforcements on many of the guitars that I setup. They step up face to back transmit if made out of the right material made the right size, and put in the right places.
Height Of Back Braces
When Martin started the adjustable Truss rod guitars in '87 they made the rear two back braces taller than the front two back braces. I generally take down the height of the rear to match the front. This allows the back of the guitar to move giving the guitar a deeper tone in general, the guitar being mahogany or rosewood.
Neck Set: $300 (most guitars) and up, call for details.