**What do you want to do with that "routed" signal? **
What's the Arduino going to do with the signal?
What are you really-really trying to do, before you go-off in the wrong direction?
I want to use an arduino to control where analogue audo signals are routed. Input them on one pin and output them on one of a choice of other pins.
Not the Arduino because the Arduino doesn't have any analog outputs.
If you don't really need to switch, you can connect multiple inputs together so you could run an audio signal into the Arduino and into an amplifier at the same time, or into two amplifiers at the same time, etc. (As a general rule, you should NEVER connect two outputs together.)
I can't find much information on using mics as anything other than sensors.
Obviously there needs to be some sort of amplifeier between the mic capsule itself and the Arduino.
Yes, you need a preamp. A microphone puts-out a few-millivolts depending on the loudness of the sound, the distance from the sound source, and the microphone sensitivity.
For example, audio mixers have built-in preamps. Soundcards and audio interfaces also have built-in preamps.
[u]Line Level[/u] (and headphone level) signals are in the ballpark of 1V (again depending on loudness, etc.). The audio signals in & out of your TV or stereo are line-level.
The Arduino analog input is 0 to +5V, which is in the same ballpark as line level (except audio signals are AC, so they swing negative).
An electret condenser microphone capsule also needs to be "powered". All condenser mics need power. Studio condensers use 48V phantom power. Electret mics run from lower voltage and computer mics get 5V from the soundcard. Dynamic mics (like the famous Shure SM57/58) don't need power (but they still need a preamp).
Since the Arduino can't read the negative-half of the AC audio waveform, the signal has to be biased at 2.5V (if it's actually an audio signal).
But are the sensor boards like the KY-038 sufficient, and having got a voltage onto the Arduino, is it simply a case of coding voltage at pin A = Voltage at pin B?
Maybe... I couldn't find the "real specs" or a schematic for that board. It has a binary digital output that goes high when the sound is above the threshold (set by the pot).
It has an analog output but I don't know how that works. It could be an amplified & biased audio signal or it could be a varying DC signal that's proportional to the loudness.