Microphone input into Arduino uno R3 I have an amplifier circuit for a microphone.The output of the circuit(the microphone signal amplified) is connected to the arduino A0 .Now the circuit works(I think ,the output voltage is 4.30 V) and the arduino serial monitor output 875 874... fluctuates with one or 1,2 or more points.The problem is that this value just goes down from 875....800.... .

Is it a correct value?(circuit taken from here http://wiring.org.co/learning/basics/microphone.html)

EDIT: If I put my finger on it the values go up a bit like 792 ,794,800
This schematic contains also the OpAmp stage for a microphone.
You could take it as reference against the design you are using.
The LM386 is basically a more integrated version, iirc.