請教一下，mic in 和 line in 有什么區別？

Microphone produces very weak signal (10mV ~ 50mV) which needs to be amplified. Therefore mic in signal goes through amplifier with high gain up to +40dB. Sometimes it's a two stage amplifiers. One is +20dB microphone boost; the other is a PGA (programmable gain amplifier) with gain range around 0dB to +20dB.
Line in signal usually needs little gain. Standard line in/out signal is 1Vrms or 0.75Vrms.

Are there any other difference such as input/output resistance/capacitance, noise consideration, THD and so on