Will connecting an electronic instrument's output to a computer's microphone input overload the computer?
In general, you won't cause any damage. A wise precaution is to turn down the volume on the instrument before plugging in and then turning the volume up until the level is adequate.

The problem is noise.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. The typical setup.

The amplifier output of Figure 1 will send out some noise irrespective of where the volume control is set.

Now imagine that the instrument is designed to give out a 1 V signal but the PC input is 50 mV mic in. You can turn down the instrument volume control to limit the signal to 50 mV but the noise level will be unaffected. The result is that the signal to noise ratio is much worse by a factor of 20.

If the noise level is unacceptable the solution is to attenuate outside the instrument.







simulate this circuit

Figure 2. Fixed resistor attenuators or variable potentiometer attenuators.

If using the potentiometer option then buy a stereo log (audio taper) pot for best results.