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Microphone Amplifier


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Look at XLR Connector in Google. It shows the balanced signal pins and the ground pin of your microphone. Shure's datasheet for your microphone also shows which pin is which.

Most of the "horrible" schematics of preamps with only two wires for the mic are for cheap toys. Your Shure professional microphone is not used in toys, it is balanced.

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You cannot connect anything directly to both inputs of an opamp because the voltage gain would be 200,000 at low frequencies which is way too high. The opamp needs to have negative feedback to reduce the gain to a usable amount. The inputs of an opamp also need to be biased correctly.

Look in Google for Opamp Differential Input Pre-amplifier Circuit that has two inputs for a balanced microphone.

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  • 2 weeks later...

The Shure SM58 provides a positive signal on pin 2 with respect to pin 3 when pressure is put on the diaphragm (when sound hits it). Pin 1 is connected to ground. To connect this microphone to an unbalanced mixer, you just connect pins 3 and 1 to ground and use pin 2 as your signal output. This is all you have when you purchase a cable with XLR on one end and 1/4" phono jack on the other end.
You will not see any difference in the output unless you are running massive lengths of microphone cables.


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