Gary Clark Jr Tulsa A guitar pickup is essentially much like a dynamic microphone coil. For decades, dynamic microphones have been sent with the voice coil attached to the primary of the microphone's transformer, and maybe not referenced to soil (‘floating'). The microphone's case is usually linked to the cable shield, which will be connected to the mike amplifier's ground (see Rane's site for more discussion).
By and big, active microphones are very quiet devices consequently of the combination of transformer isolation and healthy, hanging transmission lines during, as well as guarded, humbucking coils.
So why not instruments? Instruments are notoriously affected by noise. Humbucking pickups are merely a partial (though important!) solution. The most obvious alternative is to float the guitar collection to a healthy result, as being a microphone. The same thought was published this 2001 patent application like this Gary Clark Jr Tulsa?