Understanding guitar schematics

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Understanding Guitar Schematics.

Many guitar wiring diagrams are drawn in hard wiring form whilst some are in schematic form.

The difference is that schematics show how a circuit works whilst the others just show the layout of the components.

So, this is for people who want to be able to read schematics and know how things work. Remember that knowledge is power! Also, I hope to be able to show that by keeping effects units to a minimum your guitar will retain it's "Sparkle" in the tone.

These subjects can be as complex as you want so I have avoided going into the mathematics of it all in the hope that a simple overview will assist in people's general understanding of basic principals.

Please note that this article is for educational purposes only. Only qualified personnel should carry out any electrical work. I accept no responsibility for loss or damage, consequential or otherwise, caused through the use of information contained in this article. Nor do I encourage non qualified persons to modify or repair electrical equipment of any kind. Electricity can kill, pass any electrical work requirements to a qualified person.

Basic Principles

The circuit below shows a guitar pickup connected to a resistor. This is the simplest form of generating electricity and then using it up, the pickup is the generator and the resistor the "load". A "load" is something, which draws current from an electrical source. This simply means that the pickup generates an electrical current, which travels along the two wires and goes into the resistor and becomes heat. The current is so small and the heat generated so tiny that it could only be measured with special equipment but it is there!

In our circuit there is a red and a black wire connecting the two items. We normally show the earth (or ground,) wire at the bottom and the wire which carries the signal at the top – in this case in red.

It is also good practice to draw schematics showing the signal path going from left to right. In this example the signal starts life in the pickup and is used up in the resistor.

If it's resistance is too low the resistor will try to draw more current than the pickup can give and performance will suffer. A small resistance will "dampen" the coil's performance and the high frequencies will be the first to go. (A low resistance is the same as a high load.)

In the above circuit I have replaced the load resistor with a potentiometer (pot.). The slider can travel the length of the resistor and tap off however much of the signal is required. The signal path is shown in red and we now have the simplest guitar circuit with a pickup and a volume control. As the slider approaches earth (ground,) it will tap off fewer signals than if it is at the "hot" end.

In this circuit I have added a tone control, the symbol with double lines is a capacitor which will show less resistance to high frequencies than low ones. It is drawn in red because a signal always travels through the capacitor through the variable resistor down to ground where it is lost. If the slider of the pot is at the top of the resistor the high notes have got to travel through the whole of the track to get to ground. As we move the slider towards the bottom of the track there is less resistance to the high notes and more of them are lost to ground. When the tone pot is turned fully anticlockwise the slider is touching ground and the resistor is out of circuit. Clockwise is the full resistance in circuit. The full resistance is normally calculated to drain a negligible amount of highs.

Here is the same circuit with the addition of a bleed capacitor. Capacitors will allow treble through easier than bass. A small capacitor will only allow high treble through. The above circuit allows high treble notes to bi pass the vol. control, so that if the vol. control is not fully up some extra high treble will get through, this is the circuit used in Telecasters to give that snappy sound.

The purple line shows the path, which the high treble signals travel from the pickup up through the bleed capacitor. If the tone control were turned down then the high trebles would be lost before they got to the vol. control. The bleed capacitor is only effective if the tone control is fully clockwise (max track in circuit.)

Telecaster Circuit

This is the final standard circuit as used in Telecaster type guitars. The selector switch can select either or both pickups. I have noticed that some current USA Telecasters are not fitted with the treble bleed capacitor, to check this try turning the vol. down, if one is fitted you will notice that the more you turn it, the thinner (more trebly,) the sound gets before it vanishes.

Fender, Squier, Stratocaster, Strat, Telecaster, and Tele are trademarks of Fender Musical Instruments Corporation. I am not associated with that company. All drawings and explanations are my interpretations only and are for education and interest purposes only.

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