arduino How to make a clean amplified microphone analog to digital conversion

Hooked up an electret mic into an opamp and gave output to my arduino microcontroller. The ADC on the microcontroller converts a range of 0 to 5 vV to a 10-bit number (0 to 1023). The problem is that the output from the latter two chips is not `clean`. The analogRead() on the Arduino is always reading a non-zero value even when I make no noise in the mic. The reading reacts properly when I make noise,
arduino How to make a clean amplified microphone analog to digital conversion - schematic

but the "zero" value is non-zero. Sometimes the "zero" value even flickers throwing off the reading all the time. Hopefully that made sense. Yes I have C2 in place. It`s about 2 volts. I dont know if this makes any sense: could it be that there is some current trapped( ) in the loop between pin 2 and 6, the output and inverting input Shubham Jul 10 `11 at 0:55 The presence of C2 means that the output of the preamp will be swinging around 0V - not 2. 5V which it is operating at internally. Majenko Jul 10 `11 at 8:49 One other thing - you may want to slip a little shottky diode in between the pre-amp C2 and the Arduino input - throw away those negative voltages that you really don`t care about. One more thing I did was to add another capacitor between the analog input and ground to smooth the signal out a bit. Makes the VU meter a little less flickery. Majenko Jul 10 `11 at 8:53 Get rid of the output capacitor. That circuit was probably meant to produce a signal around zero, so the capacitor is there to block the 1/2 Vdd offset. However, the microcontroller wants to see the signal centered around 1/2 Vdd, so just get rid of the capacitor. Microcphones do need a lot of gain. Electrets can be sensitive, but you still might need a voltage gain of 1000. The gain in your circuit is the ratio of R5 to R2, but this only works within limits of what the opamp can do. The values you mentioned above would give you a gain of 5000....

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