3

The problem is likely not with your preamp itself (the circuit is basically OK), but with the power supply and gain setting. Using the internal 5V from your PC (or USB port) for a mic pre is pretty much a no-no. There is almost certainly switching noise in that power rail which will be very audible. (The mic output is typically a few mV, perhaps 10-20mV or a ...


1

A lousy old lM358 is never used for audio because it is noisy (hissss), has a poor slew rate above 2kHz and produces crossover distortion. Your very low value of 1k tor R4 (because the opamp is inverting instead of non-inverting) reduces the output level from the mic to 1/3rd so the amplification from the opamp must be increased which increases its noise.


1

As others have hinted at, the LM358 is ancient and far better modern parts are available. Put "low noise amplifier" into your favourite parametric search. You might select something like the AD8691, a 5V supply low noise amplifier. Secondly, power supply noise is critical. You're going to need to experiment with more filter capacitors and possibly ...


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