The use of the correct cable is very important to the performance of your equipment. The following describes the different kinds of cable and their use.
Instrument cable is shielded which means that it has a inner wire that is completely surrounded by another wire. The outside wire is referred to as the shield. The shield serves the purpose of directing airborne interference, like radio waves or fluorescent light noise, away from the cable. The shield protects the inner wire from these waves. Use this cable in low level applications to connect between components such as guitar to amp, effects to amp, or any areas where "power" is not involved. Do not use Instrument cables for speakers, as amplifier damage or poor performance can occur.
Speaker cable has two parallel multi-strand conductors. It is designed to carry large amounts of energy. It should be used between the power section of your equipment and the speakers only. The size or gauge of the wire also has an effect on the performance of your equipment. The amount of power used and the length of the cable determines the gauge of wire that you need. Generally, the larger the wire the better. Note: Smaller awg number = larger wire diameter.
There are two kinds of wire used for microphones. Professional microphones use balanced (3 conductor) cables and low cost microphones use cable that is the same as instrument cable (2 conductor). The advantage of the 3 conductor cable is it has 2 wires that carry the signal and a shield that acts only to carry away the airborne interference. This design allows very long cable runs of over 1000 feet without noticeable signal loss. The 2 conductor wire should not exceed 20 feet or signal loss and increased noise may occur. If you have a balanced microphone and need to connect it to a 2 wire system (1/4" jack) you should use a transformer at the 1/4" end to convert the signal from balanced to unbalanced. Without the transformer, although it will "work", you have the same effect as a 2 wire system but with some frequency loss. Also longer cable lengths should be avoided.