Oh and the circuit you posted does not even work, like most of the stuff I have found so far on the net:)
The circuit is quite standard, can't imagine why it should not work.
Have you checked the DC levels on the in and output ?
You need to increase the value of the 16k resistor to get the default output level beyond 3 Volt, probably to about 1.5 to make the output swing between 0 and +3 Volts. The 16 and 8 k resistors build a divider chain. Leave out the bottom 5k6 and replace the 16k with a 40k (default E12 range 8k2 and 39k will do).
Check the output DC level of the opamp and the DC level of the inputs, they should all be around 1.5 Volts with 9 Volts as supply.
It is all rather basic opamp and ohms law stuff.
Build your circuit step by step:
Set your power supply to a stable 9 Volts, if it has a current limit set it to 100 mA max, build the resistor divider and measure the voltage on the bottom resistor (the 8k one) is it 1.5 Volts ? If so, connect the opamp, pin 4 to ground, pin 8 to +9 Volts. Connect the divider chain to the + input, connect the 10k resistor from output to the - input. Check the DC levels after switchon, they all should be around 1.5 Volts (+ input, - input and the output) then add the other components.
The micrpophone in this circuit is an electret one which gets its power through the output pin, the resistor will limit the DC current and the voltage to the microphone, the 0.01u capacitor will block this 9 Volts to the rest of the circuit.
Also remember that the LM358 is a DUAL opamp, so inputs and outputs all are on the same side for each of the two opamps inside. Connect the inputs of the unused opamp to gnd, leave the unused output open.
Gert
Can anybody tell me what is the maxium negative voltage I can apply on the power supply pins
I think that is pin 4 right
Was gonna use the MAX232 to give me the negative voltage..
Kinda confused on if VCM means that the max negative volts that can be applied?? since it is only - 1.5 volts -2 volts.
Max postive is +32 volts is max neagtive -32 volts.