Article #1: Guitar strings gauges and how they affect your setup.
The pitch a string produces when plucked if defined by the following attributes of the string.
If we take a standard set of 9s as a reference then the 1st string is 0.009" in diameter.
If we tune the string to the standard E, the string will be under a certain amount of tension. This tension will pull on the neck and cause an amount of upbow to be pulled into the neck.
If we raise or lower the pitch of the string we are varying the tension in the string and also changing the amount of bow produced in the neck i.e. If we lower the pitch (less tension) the neck will lose bow. If we raise the pitch (more tension) the amount of bow in the neck will increase.
If we were to swap the 0.009" string for one of 0.010" diameter things will change because the 0.010" string is thicker and heavier. The 0.010" string will require more tension than the 0.009" string to be tuned to the same note. Therefore a guitar strung with a set of 10s and tuned to pitch will have a neck under higher tension than a guitar strung with 9s at the same pitch. Due to the higher tension the guitar with 10s will also have more upbow in the neck than the guitar with 9s. Of course the opposite of this scenario is that if we moved from 10s to 9s the bow in the neck will be reduced (less tension).
This is why a guitar needs a truss rod adjustment when a player changing string gauges. The truss rod needs to be loosened or tightened to balance the pull of the string tension. If a lighter set of strings has been fitted then the bow is reduced and there will be a possibility of fret buzz. If a heavier set of strings has been fitted the bow is increased and the string heights will increase making the guitar uncomfortable to play.
It is also worth noting that changing string gauges also affects a guitar's intonation this will also need correcting.
Another factor that infulences the pitch of a string is its length.
The scale length of a guitar is defined as the distance from the front face of the nut to the centre of the bridge saddle. Most bridges are staggered to correct the intonation so it easier to think of the scale length as the distance from the front face of the nut to the centre of the 12th fret multiplied by 2.
A Fender Stratocaster has a scale length of 25½" whereas a Gibson Les Paul has a scale length of 23¾". These are not the only two guitar scale lengths, but they are the most common. Bass guitars with 4 strings have a scale length of around 34", whereas 5 and 6 strings basses may have a scale length somewhere in the region of 36" or a little longer.
A 0.009" string tuned to pitch on a Les Paul will be at a lower tension than the same string tuned to pitch on a Stratocaster. This due to the difference scale length between the two guitars.
I advise players who own both a Strat and a Les Paul to go a gauge heavier on the Les Paul than the gauge they use on their Strat to maintain the "feel" across both instruments.
If a player is wishes to play down-tuned e.g. Eb tuning or lower, then due to the fact that the tension will be decreased, thicker strings should be used i.e. Use one gauge heavier for every semitone you down-tune.
There are commercially available sets that give players who down-tune to extremes very thick strings to keep the tension usable on their guitars.
It should be noted that if you want to temporarily down-tune your guitar you may run into problems as your guitar setup will "become wrong" due to the decrease in string tension (don't try this on a guitar that has a tremelo unit as this will cause even more problems since the tremelo is also balanced against the string tension).
String Gauges In General
A player should experiment with different strings gauges for the following reasons.
Remember changing your string gauge (sometimes even changing the brand of strings) affects the setup of your guitar i.e.
In short if you change your string gauge you will need to get your guitar setup to maintain optimum performance and playability.
Paul Waring April 2015.
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