Do It Yourself Setup
Even a brand new guitar right from the factory will need a little TLC to play the way you want it to. The frets may need to be leveled or glued and you should leave that to a qualified repair person, but you can do a couple of things that will quickly improve playability.
Neck/Truss Rod Adjustment
First determine that the neck is straight. This is best done using a straight edge and feeler gauges, but there’s a quick and reliable way to do it without those tools: Hold the guitar in the playing position without stressing the neck, upright on its edge as you would standing or sitting to play – laying the guitar on its back without supporting the neck will allow it to deflect backwards, supporting the neck in first position will increase positive warp . This is especially true for thinner necks such as on most electric guitars. With a left hand finger press the 6th string down at the first fret and with your right hand press the same string at about the body joint (vicinity of the 14th to 16th frets)with your baby finger. Press the string down just so that it touches the tops of the frets – pressing harder so that it is touching the fingerboard will deflect the main length of the string upwards. Continuing to hold the string down at both ends, stretch your right hand index finger toward the middle of the string, (vicinity of the 7th or 8th fret) and press the string down to the fret. If the neck is properly adjusted there will be a tiny space between the string and the fret. If there is no space the rod may be over-tensioned, producing reverse warp, while a large space between the string and the fret indicates excess positive warp or so-called “relief.” Sighting down the neck is nearly useless; perspective distortion complicates your view, only the grossest warp is perceptible and you are seeing the edge of the fingerboard – neck shape along the tops of frets may be quite different as noted below.
The process can be repeated for each of the six strings. This may reveal that the degree of warp is not the same across the width of the fingerboard. Some necks even show positive warp along the bass side with reverse warp along the treble side. This situation, and compound or “S”-warp, indicates the need to re-cut and true the fingerboard surface.
Using a String as Straight Edge
Most rod systems have a hex nut (external), allen hex (internal) or flat screwdriver blade adjusting fixture. Gibson instruments have a 5/16″ (external) hex fixture located under a cover at the peghead. Earlier Fenders have a slotted fixture located at the upper end of the neck, more recent ones have a 1/8″ Allen (internal) hex drive located at the peghead.
A properly designed rod system should make a perceptible change in neck shape with a 1/4 to 1/3 turn of the adjuster. However, fewer than half of all rod systems work with reasonable efficiency and many affect neck shape unevenly or not at all!
In the presence of too much warp turn the adjuster 1/4 to 1/3 turn clockwise. Next, flex the neck, pressing down at both ends with support under the middle and observe the effect, repeating the process as necessary. (Flexing the neck will settle it into its new shape immediately – without flexing the neck may not settle down for hours or even days.) Following this procedure will insure that you do not harm the system. If a full turn does not produce the desired result seek expert assistance.
In the presence of reverse warp turn the adjuster counter-clockwise and flex the neck, pushing down near the middle while it is supported at each end. Although rare, some necks show residual reverse warp even with the rod fully relaxed – if so, call for help.
In making these adjustments it is sometimes helpful to twist the neck a little by grabbing it at the peghead to fully settle it after initially flexing it at the middle. If you follow these suggestions you will not risk damaging the instrument.
The neck, along with the entire instrument (especially acoustic types) reacts to changes in humidity. Higher humidity makes most necks act as thought the rod was tightened, sometimes enough to produced reverse warp. At lower humidity the opposite occurs and warp often increases, hence neck rod adjustment may be required at least twice a year or more often to maintain optimum setup specs.
Note that with increased warp, string elevations (action) increase, with less warp elevations go down. The fact that the tops of acoustic guitars go up and down with changes in humidity complicates analysis of this aspect of setup resulting in (usually) higher action in summer and lower action in winter. The procedures described above will allow you to isolate how much of those changes in action are due to varying neck warp.
String height adjustment at the Bridge
The distance between the strings and the tops of the frets is the primary reference point related to “action” or playability. Upper register elevations are affected primarily by adjustments at the bridge. Most electric guitars and bases have bridges that allow for user adjustment of string elevations in the form of screws or other threaded fixtures that raise/lower the entire bridge (as on the Gibson “Tune-o-Matic” bridge or the individual bridge saddles (as on most Fender instruments.)
While these adjustments can be made by feel or eye, a precision ruler graduated in 0.010″ is useful. On electric guitars string elevations at the 12th fret range from 0.040″ (1st string) to 0.070″ (6th string). On acoustic steel-string guitars octave elevations range from 0.080″ (first string) to 0.10″ for the sixth string and for nylon-strung instruments octave elevations range from 0.10″ (first string) to 0.14″ for the sixth string. Those are average specs. – player technique, music style and string gauge and type may accommodate a lower setup or require it to be higher. There is no supposedly “correct” or “official” setup spec. for any particular instrument type or make as some manufacturers would have you believe.
The change in elevation from the 1st to the 6th string should be evenly incremental so that no individual string is very much higher or lower than its neighbors on either side. To find the lowest practical elevations lower the bridge/saddles heights until fret buzz occurs everywhere even with a light attack then raise the bridge adjustment until no buzzing occurs.
Make small adjustments and retune at each step. Where the height of the saddles is not individually adjustable and the string heights are uneven this adjustment is made by filing the grooves where the string rests in the saddle – a job for an experienced technician – Don’t try to do this yourself.
String height adjustment in First Position
Regulation of string heights here is effected by filing the string grooves in the fingerboard nut – definitely a job for an expert requiring the use of feeler gauges, but the process is described briefly. This sets up 1st position action almost to the exclusion of the adjustments made at the bridge. Typical elevation specs. between the string and 1st fret are from 0.012″ (1st string) to 0.017″ (6th string) on electric guitars and 0.015″ – 0.020″ on acoustic types. These specs., like those for the octave elevations described above, are approximate and may require adjustment to accommodate different string gauges and individual player technique.
Bridge Adjustments Affecting Intonation
Because of stiffness factor the vibrating string acts as though it is shorter than the actual string length causing notes in the upper register to be sharp. This is compensated for by making the string longer than its theoretical length. Since this is related to stiffness, compensation is minimal for the thinner (more flexible) strings and greater for the thicker (stiffer) strings.
An electronic tuner is useful here. Play the open string harmonic at the 12th fret and compare the fretted note to it. If the fretted note is sharp compared to the harmonic the string needs to be longer – if it is flat, make it shorter. Repeat the procedure at the 19th fret and tweak the string length adjustment if necessary. Inability to set the intonation at both the 12th and 19th frets with the same string length adjustment is likely evidence of inaccuracies in the fret scale Contrary to popular misconception, intonation inaccuracy in the upper register has nothing to do with stretching of the string. Stretch Factor affecting intonation is negligible near the middle (octave) of the string. However, stretch factor causing sharpening of notes is to be reckoned with near the end of the string in 1st position.
Compensated Fingerboard Nut
Absent compensation of the fingerboard nut location relative to its theoretical position first position notes will be sharp – most noticeably in the first two frets fading to negligible above the fourth fret. This effect is exacerbated if the fingerboard nut is mislocated flat. Adjusting fingerboard nut location is a job for only the most expert technician. Typical compensations to optimize first position intonation are 0.17″ sharp of the theoretical position for electric guitars to o.025″ for acoustic instruments.
Guitar pickups are electro-magnetic devices and therefore subject to the inverse square rule: if you double the distance between the pickup and strings you’ll get one quarter of the output strength.
If you want maximum output and, to promote distortion, operate with the pickup as close to the strings as possible without the strings hitting the top of the pickup, 0.10″ or so. For lower output and clean sound adjust the pickup-to-string distance to 0.20″ or more.
Overall pickup height is adjusted via the pickup mounting screws, 2-4 depending on the type of pickup. It is sometimes useful to adjust the pickup so that it is closer to the strings on the treble side than on the bass side since the fatter strings produce higher output than the thinner ones. Individual pole screws, such as in the Gibson Hum Bucking type allow for some adjustment of output among the individual strings.