Home
Shaping Tone
Intro to Wiring
Modified Guitar
Store
Modifications
Wiring / Soldering
Custom Guitar

Introduction to Guitar Wiring

 

All guitars have the same wiring theory associated with them.  They all consist of the source (pickups), the path (wires and switches), and the load (resistors and capacitors). There are an unlimited number of modifications that can be done, given pickups, wood type, wiring schemes, and the physical type of capacitor, or the amount of resistance the potentiometers have.  A basic single pickup wiring diagram is pictured below to show the role of the volume and tone potentiometer or pot.

When the volume and tone knob are turned all the way up the small alternating voltage,or signal, produced by the pickup has an easy route all the way to the output. There is, however, a small drain of tone existing for that particular pickup and resistance its connected to at that time.  When the tone pot is turned down, decreasing it's resistance, the high frequency signal finds an easier path to the ground connection connected to the tone pot.  This change of tone is taking place at a different cut-off point as the pot is turned from up to down.  When the tone pot is all the way down, the capacitor’s reactance is the only resistance, and a vast majority of highs gladly trickle through to ground and are never heard at the output.  The picture below shows the pot’s turned down to their half way position.   

The value of the pot also plays a role on the tone of the guitar.  The larger the resistance is, the more tone that is transferred to the guitar's final output.  You will find the pot's value sets the output volume of a guitar.  With the two 500 K ohm pots pictured below turned to their maximum, the total amount of resistance the pickup will see to the output is 250 K ohms, since the resistance's are in parallel.  A larger pot value of 1 Meg ohm, resulting in a 500 K ohm total,  can be used as well to allow more of the pickups sound, highs and lows, to make it to the guitars output without being drained to ground.  The value of the pots you choose is usually preference, but most pickups  usually specify with included wiring diagrams the best match.  A total bypass circuit can be added to eliminate the pot’s from the circuit, so that all possible tone is transferred to the output.  Check out the Modifications link for the bypass circuit.

 

If it hasn't become obvious yet, the ground connections in your guitar are a common point where the signal or voltage is trying to go to complete the circuit.  The output jack of the guitar is also grounded to the guitar and through the cable grounds to your amp and effects.  With all pots turned all the way up the voltage of the signal is applied across the pots resistance, the  small amount of current is flowing to ground to complete the circuit.  That voltage is present at the output of the guitar, then it is amplified.  The simplest way to describe this is by Ohms Law:  V = I x R, where V is voltage, I is current, and R is resistance.  When R is zero, so is the voltage or signal applied to it.

With grounding , especially in a guitar, it is very important to make sure all of the ground points in the circuit share the same easy access to the common ground point in the guitar.  If there are ground points that have different amounts of resistance to the "true ground" you are going to get noise.  The technical term for this condition is a Ground Loop.  Ground Loop is defined as  a current, generally unwanted, in a conductor connecting two points that are supposed to be at the same potential, often ground, but are actually at different potentials. Ground loops created by improperly designed or improperly installed equipment are a major cause of noise and interference in audio and video systems.  Most electronics require that the ground connection also be present through a metal box surrounding noise sensitive wiring and components.  Radio Frequency waves that make up noise or radio interference can not penetrate the grounded enclosure.  It’s important to note that when looking at electronic schematics, such as the ones I have designed, you will see a ground symbol repeated all over the diagram.  These common ground symbol represent a common point of conductivity all over the circuit.  

There are some different approaches to this that I have found and I have used a unusual approach in my own custom guitar.  The star grounding system seems to be one of the best ways that I have seen, since all ground wires themselves get soldered at a single point on the guitar.  I have also seen the ground wires being chained from one component to another to get them all electrically connected.  The new approach to this that I used was an attempt to get the entire shield cavity of the box and component wiring down to one common connection that has a very low resistance throughout.  For example after the circuit was built I found with a digital voltmeter that between any distant point in the circuit, the ground reads less than 0.0 ohms, which should yield no audible noise.  On any typical, non-copper wire, I have found resistance readings of about 0.7 ohms for 7 inches of wire or conductive tape.  This higher resistance is a result of the different metals that were used to make it.  This cheaper “alloy” utilizes little, if none of the conductivity of pure copper.  Using a solid copper buss wire and solid copper tape, I can easily measure 0.0 ohms for well over 7 inches of conductor in the circuit.  This buss wire is a solid copper wire measuring about 6 inches total.  The buss wire is soldered to the top of the three push pull pots and extends down to the nut of the last pot, bolted tightly, and is very close to the copper shielding on the pick guard.  This allows all ground wires to be soldered to this wire anywhere, and maintaining a very low resistance from the end of the wire to any point on the copper shielded pick guard. Copper also proves to be a better conductor than Lead and Lead Free solder. For an example the order of metals from highest to lowest conductivity is as follows ,multiplied by 1,000,000 Siemens per meter. Siemens is unit of conductance just like  that Ohms is a unit of resistance.   Siemens  is just the reciprocal of resistance (1 divided by the resistance).  One of the main reasons that conductance in Siemens  is used, is that all kinds of details of a circuit can be calculated without knowing any current or voltage values.  You will notice that gold is not the best conductor.  It’s primary purpose in cable plating Is to provide a corrosion resistant surface.

 

Rank of Conductivity

 

Silver - 62.1

Copper - 58.5

Gold - 44.2

Aluminum - 36.9

Zinc - 16.6

Nickel - 14.3

Tin - 8.7

Lead - 4.7

Mercury - 1.1

 

 

 

 

 

How Series Connections Work

Series connections for two coils in a guitar's pickup combination have the highest output and fullest sound.  In this case with whichever components are connected, they are linked together in a daisy chain.  The total inductance and resistance of a coil is just the sum of the two coils.  The same rule applies to resistors.  For example if a 10,000 ohm resistor is in series with a 1000 ohm resistor  the total would be 11,000 or 11k ohms. Capacitors behave exactly the opposite, two capacitors linked in series would have a total capacitance and resistance that is their product divided by their sum. This is not a typical way to  hookup a capacitor.  When I say a coil or a capacitor has a resistance, I don't want you to take that term "resistance" literally.  The resistance I am describing is an over simplification of a characteristic that is actually called reactance.  A capacitors reactance is referred to as XC and a coils reactance is referred to as XL.  This value of reactance is the value of resistance each individual frequency sees a capacitor or inductor as.  This is why caps and coils are so useful.

 

How Parallel Connections Work

For parallel connections in a pickup combination the overall output of the pickups is reduced and the sound is thinner.  I have found this combination to be very useful to take my Seymour Duncan “hot” pickups down a notch.   For example, using the same 1000 ohm and 11,000 ohm resistors, the total would be 909.09 ohms.  A general rule of thumb to remember is that with any two resistors in parallel, the total will always be less than or equal to the smallest resistor.  The capacitor’s behavior is also the flip side of the resistor or inductor.  Two capacitors connected in parallel have a value equal to their sum. When pickups are connected like this they are no longer humbucking.  I have seen many contradictions to this as well, but if you notice in the wiring diagram above, the connections are crossed, which reverses the phase relationship of one pickup to another.  This cross is used to accomplish a parallel connection in one switch mode then allow series in another. To try to keep the pickups in phase you can connect the red to the white, but if you connect the black wire to the green wire (ground) you will get no sound at all.  The only way to get around this is to have one side hardwired positive and the other side grounded.  I would rather stick with the switches, myself.  

This Diagram shows that Seymour Duncan and Dimarzio use a different color code scheme with the same wire colors, black, white, red, and green.  With Dimarzio the difference is red for black, black for white, and white for red. Duncan and Dimarzio both are used widely for the ease of coil tapping in a humbucker.

 

A Digital Multimeter like this is a necessity for troubleshooting electronics and wiring.  You can find these in all different price ranges, and they don’t have to have a lot of bells and whistles to be useful to you.  The pictured DVM has certain useful features such as a capacitance and inductance readout for a small range of components, but is also very old as you notice it comes with a floppy disk. One of the most useful features in the voltmeter that you will use for guitar electronics is the ohm meter or the continuity meter.  You can use these settings to verify the connections of switches, or seek out bad connections that have excess resistance or no continuity at all.  

Home

Copyright 2010 © Guitarhotrod.com. All rights reserved

Guitarhotrod .com is not affiliated with any of the mentioned guitar manufacturers.

 

 

Click Here to Find Guitar Insight

pot graph.JPG

A Word on Potentiometers

An important thing to understand when selecting a potentiometer to put into your guitar is the pot’s taper.  The relationships of the different types of pots is shown in the graph vs a typical logarithmic curve, which would be the ideal curve for audio, but is impossible to achieve with a pot so far.  If you noticed, audio and custom taper pots consist of linear relationships fused together.  Those sections are also fused together on the pot itself.  For example there may be three different resistive sections on a pot and they are fused end to end to resemble a perfect log taper.  Linear pots aren’t sought after very much for audio applications such as a guitar.  They don’t offer the control you would expect to hear when turning the knob.  To identify whether a pot is linear or audio, a good indication is turning the pot halfway and measuring the resistance.  If the resistance is half of the total, you have a linear pot on your hands.  Pots are also marked with the standard A and B.  A is for audio taper and B is for linear taper or custom variations that are just two linear tapers put together.  Be careful because the old standard was just the opposite, but if it is a new pot look for the A, audio taper.  One of the best pot manufactures is CTS, and possibly alpha, if it is a good quality made pot.  You can also just order the Dimarzio brand, which is varied who makes it from time to time due to Dimarzio selecting quality parts.  

Digital Multimeter