Mesa Electra Dyne A guitar collection is actually much like an energetic microphone coil. For decades, dynamic microphones have been wired with the voice coil mounted on the primary of the microphone's transformer, and perhaps not introduced to ground (‘floating'). The microphone's case is usually connected to the cable shield, that will be linked to the mike amplifier's soil (see Rane's site for more discussion).
By and big, active microphones are very calm units as a result of the mixture of transformer isolation and healthy, suspended indication lines for the duration of, as well as shielded, humbucking coils.
Therefore why not instruments? Instruments are once affected by noise. Humbucking pickups are merely an incomplete (though crucial!) solution. Well-known answer would be to float practicing the guitar pickup to a balanced output, being a microphone. A similar idea was printed that 2001 patent application like this Mesa Electra Dyne?