R2 =  K 
                                                R3 =  K
                                                R4 =  K
                                                C1 =  nF
                                                C2 =  pF
                                                C3 =  uF

                                              

 
   

The preamplifier (also known as the preamplifier) refers to the audio (such as AUX, MIC) signal amplification to the power amplifier can accept the input range, preamplifier function has two: first, to select the desired sound source signal, and amplify to the rated level; second, to carry out a variety of sound quality control to beautify the sound. The basic components of the preamplifier are: sound source selection, input amplification and sound quality control circuit. The function of the source selection circuit is to select the desired sound source signal into the later stage, while closing other sound source channels. The function of the input amplifier is to amplify the sound source signal to the rated level, usually about 1V. The function of sound quality control is to control the frequency characteristics of the sound system to achieve high-fidelity sound quality, or to modify and beautify the sound according to the interests of the listener.