microphone pre-amplifier
Due to the high sensitivity of microphones, only voltages in the millivolt range are generated when sound pressure is converted into electrical signals. In order to avoid interference signals, these millivolt signals can already be preamplified in an integrated microphone preamplifier and routed via the microphone cable. Other microphone preamplifiers are stand-alone amplifiers that already have various elements for sound manipulation.
The integrated microphone preamplifier requires a supply voltage, which it receives either from a battery or its own supply from the mixing console. This supply voltage is set up as phantom power so that all microphones are operated and not damaged. The supply voltage ranges from 9 V to 48 V, with the 48 V usually being used. As an alternative to phantom power, the microphone preamplifiers used to be supplied via the audio power supply.
Important characteristics of microphone preamplifiers are the number of channels, linearity of frequency response, freedom from distortion, input sensitivity, which can be >60 decibels unloaded( dBu), gain, which can be 80 dB or more with an output level of >20 dBu, and noise voltage.