additional preamplifier

It is a preamplifier added to this circuit . Its input terminal is connected to the output terminal of the graphic equalizer, and its output
terminal is connected to the input terminal of Figure 4-62. In the figure, Icl and Iba are buffer stages, which function to isolate the amplifier and the display to prevent the display from
flickering and displaying pulses that interfere with the amplifier and introduce unnecessary noise . I island is a voltage amplification stage, and
the gain can be adjusted through RP. Its adjustment range is 0r13. SdB, the input sensitivity at maximum gain is 90mVolC,
LM324 , TL084, etc. can be used.