Pre-Amp Circuit

Front of the amplifier is done by the Op-Amp A1, this is the amplifier A1 is actually a time, with the intention of utilizing the high input impedance, about the size of 1M, from one specification data suggest op-amp for use with high-frequency dynamics, the input impedance is too large will degrade its stability, therefore the potentiometer (Pot1) of 47k is used to ensure impedasi input circuit, an audio standard value (real 50k), if the reader wants an application with a larger input impedance, use the value of Pot1 higher, it is recommended to not exceed 220K. Pot1 is also acting as a regulator of the audio volume level.