Powered Guitar Cabinet A guitar pickup is essentially much like a powerful mike coil. For decades, active microphones have been wired with the style coil mounted on the primary of the microphone's transformer, and maybe not introduced to surface (‘floating'). The microphone's case is typically linked to the cable guard, which is linked to the microphone amplifier's soil (see Rane's web site for more discussion).
By and big, active microphones are extremely calm devices as a result of the combination of transformer isolation and balanced, hanging transmission lines all through, as well as guarded, humbucking coils.
So why not instruments? Instruments are notoriously plagued by noise. Humbucking pickups are just a partial (though crucial!) solution. The most obvious answer is to float your guitar pickup to a healthy productivity, being a microphone. A similar strategy was printed this 2001 patent software such as Powered Guitar Cabinet?