Just like the mics themselves, microphone cables are available in high impedance or low impedance format and therefore it is important to match the correct cable with the correct type of microphone. There is also a choice of interface depending on the facilities available on your mixer or PA amplifier. The choices are either a ¼" jack plug or an XLR 3-pin interface.
Low impedance cables are more suitable for long cable runs such as where microphones connect to a multi-core stage-box system as a high impedance line that is interacting with outside electrical interference will act more like an "antenna" than a low impedance line and thereby attract noise interference.
Keeping impedance low and using quality cables can be important issues for maintaining wide frequency response in long cable runs. However, the impedance of the transmission line (or cable) is affected by the impedances of the devices that are connected to it.
A high impedance microphone or guitar will usually output a greater signal (voltage) than a low impedance microphone. This high impedance signal works fine and even has some advantages in a sound system as the mixer or amplifier doesn't need to boost the signal as much. Therefore, any noise on the line remains un-amplified and this results in an improved signal to noise ratio.
