Humbucking
Encyclopedia
For the purposes of this article, "hum" is defined as "an unwanted signal, generally at the frequency of the local A.C. electrical supply" (Mains hum
).
The process by which electrical voltage and/or current (signal) levels are reduced by combining them with otherwise identical signals that are shifted or reversed in phase, is called "bucking".
Humbucking is a process in which "hum" that is causing objectionable artifacts, generally in audio or video systems, is reduced or eliminated (bucked) in electrical and/or electronic systems and/or devices. This is a term used when the reduction is accomplished through the use of devices that introduce a 180 degree phase shift only in the undesirable portion of the signal in such a way that, when the modified signal is combined with the original, the unwanted part of the signal is reduced to a point where it is no longer noticeable and the desired part of the signal is not noticeably affected.
This is also described as common-mode rejection, and is the phenomenon which dictates the use of balanced line
s (twisted pair
s) in communication cables.
Mains hum
Mains hum, electric hum, or power line hum is an audible oscillation of alternating current at the frequency of the mains electricity, which is usually 50 Hz or 60 Hz, depending on the local power line frequency...
).
The process by which electrical voltage and/or current (signal) levels are reduced by combining them with otherwise identical signals that are shifted or reversed in phase, is called "bucking".
Humbucking is a process in which "hum" that is causing objectionable artifacts, generally in audio or video systems, is reduced or eliminated (bucked) in electrical and/or electronic systems and/or devices. This is a term used when the reduction is accomplished through the use of devices that introduce a 180 degree phase shift only in the undesirable portion of the signal in such a way that, when the modified signal is combined with the original, the unwanted part of the signal is reduced to a point where it is no longer noticeable and the desired part of the signal is not noticeably affected.
This is also described as common-mode rejection, and is the phenomenon which dictates the use of balanced line
Balanced line
In telecommunications and professional audio, a balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits. The chief advantage of the...
s (twisted pair
Twisted pair
Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs...
s) in communication cables.
Applications
Some common applications of this process are:- HumbuckerHumbuckerA humbucker is a type of electric guitar pickup, first patented by Seth Lover and the Gibson company, that uses two coils, both generating string signal. Humbuckers have higher output than a single coil pickup since both coils are connected in series...
s (Humbucking guitar pickups). - Humbucking microphones (the Sennheiser MD421, Shure SM63 and others).
- Humbucking transformers or coils used in video systems.
- Telephone (and other audio) system and computer communications wiring.