Chet Atkins Guitar Lesson A guitar pickup is basically just like a vibrant mike coil. For many years, active microphones have now been wired with the voice coil attached to the primary of the microphone's transformer, and not recommended to soil (‘floating'). The microphone's case is usually connected to the cable guard, that will be linked to the mike amplifier's surface (see Rane's web site for more discussion).
By and big, energetic microphones are very quiet units consequently of the mix of transformer isolation and healthy, flying sign lines during, as well as protected, humbucking coils.
Therefore why not guitars? Guitars are notoriously overwhelmed by noise. Humbucking pickups are only a partial (though essential!) solution. The most obvious answer is always to float the guitar collection to a balanced output, as being a microphone. A similar idea was published that 2001 patent application such as Chet Atkins Guitar Lesson?