Ampeg Bass Cabinet A guitar collection is basically just like an energetic mike coil. For decades, active microphones have now been sent with the style coil attached to the primary of the microphone's transformer, and perhaps not referenced to floor (‘floating'). The microphone's case is typically attached to the cable guard, which is linked to the microphone amplifier's ground (see Rane's website for more discussion).
By and big, energetic microphones are very quiet units consequently of the combination of transformer isolation and healthy, hanging indication lines all through, in addition to shielded, humbucking coils.
So why don't you guitars? Guitars are notoriously affected by noise. Humbucking pickups are only a partial (though important!) solution. The most obvious option is always to move the guitar pickup to a balanced production, just like a microphone. The same idea was published this 2001 patent request like this Ampeg Bass Cabinet?