I have wonder How i can build 1 Preamp using 2N9304 Transistor. and the output should be connected to the Analogs Pin. I am trying to very basic guitar effects. But i dont know how to build preamp.
Well first you have to deal with a hardware restriction, an arduino analog input pin (as well as digital pins) cannot safely handle AC voltages, which is what a audio signal is. The negative part of the waveform has to be biased such that the whole audio waveform is contained in a 0 to +5vdc voltage range that an arduino can handle electrically. A single transistor circuit is a rather limited way to amplify and bias a low level audio signal. A two stage op-amp in a 8 pin DIP package is probably the minimum way to go. Second, what do you want your program to be able to do with this analog audio signal? An arduino is pretty limited in what it can extract from such a signal and limited SRAM space makes storing such sampled information very difficult.