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Potentiometer Volume Control

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The most logical thing to add to an electric guitar with only one pickup would be a volume control. curious how the volume control or volume potentiometer actually works? Read on...

The diagram below shows a one pickup electric guitar connecting to an amp. It also shows what happens if a piece of conductive material connects the hot lead to the ground lead. Infact nothing would happen. your guitars signal would go into the ground network rather then making it to the guitar amp gain stages via the hot wire (tip of the guitar cable). Once the connection between the hot wire and ground wire is broken then the signal will once again make it to the amp and you will hear your guitar play through the amp again.

guitar signal going to ground

The diagram below shows what happens when a resistor is connecting the hot and ground wires. If you do not know, resistors are tiny components which resist electricity. The value of the resistor determines how much electricy or in this case how much of the audio signal makes it to the amps gain stages. So with a resistor in this circuit only part of the audio signal will make it to the amps gain stages.

guitar signal demonstration

The diagram below shows a potentiometer. A potentiometer or pot is a variable resistor. In the case of guitars the common values (in Ohms) that are used are 250K, 500K, 1M (more on this subject). If we say that the pot in the diagram is a 250k pot then its resistance when the knob is fully counter clock wise (or zero on the guitar volume knob) will be zero Ohms (the measuring unit of resistance). If the knob is fully clock wise (or 10 on the guitar volume knob) then the resistance is 250k Ohms. The audio signal is looking for the path with the least resistance and if your volume pot is set to zero then there is nothing stopping the signal from going to the ground network causing no signal to make it to the amps gain stages. The ground network offers less resistance than the amps gain stages so the signal if given the chance will always go to the ground network. As the volume knob is turned clockwise the resistance of the pot goes up and the added resistance between the hot and ground leads will cause the audio signal to go back to the amps gain stages.

potentiometer volume control

Here is how the wiring of a volume pot actaully looks. The input is the hot wire from the pickup. The output is the hot wire going to the amp via the guitars output jack (soldered to the lug of the jack which contacts the guitar cables shaft). The ground is the black wire in the above diagram.

potentiometer volume control diagram

Now here are Two Diagrams of the exact same schematic. Both Diagrams show exactly how to wire a one pickup, one volume pot guitar. The left side diagram shows how ground networks are often shown in guitar wiring diagrams, with implied knowledge. Many guitar wiring diagrams assume that you know where to wire the ground wires and often just show the positive wires because it is easier to visualize the path of the audio signal. The general rule of thumb for grounding is that if you see those grounding symbols (the antenna-looking symbols in the left side diagram) then it should be a ground wire which goes to the case of the volume pot. This is what the green wires demonstrate in the right side diagram.

volume potentiometer wiring volume pot wiring schematic

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