Now , with my teacher I did a circuit after the previous preamp and I have in the input of arduino a signal between 1v and 4v more or less because with the picking up of the guitar sometimes if I play hard the string I can have 5v so from 1v to 4v would be enough. Now the second problem is to use a librarie that says me what frecuency is on arduino input. I tried with ArduinoFFT and saw one FIx_FFT..
any help!? thanks!