Three definitions of mass loops
Ground loop or ground loop
Qhen connecting two, or more, earthed audio equipment (e.g. a source and an amplifier), the reference potential with respect to earth of one (zero, in the ideal case) may be slightly different from that of the other; thus creating apotential difference (voltage) and thus a circulation of current through audio cablesconnecting the two devices.
Ground loops
Ground loops(in Italian, mass rings) are special situations that frequently occur whentwo or more devices share more than one earth or ground connection. This frequently occurs when at least two elements in an audio chain are grounded (or at least have a common ground, as is often the case with car audio devices). Ground loops are one of the most frequent causes of hum between audio devices.
The ground loop, known in English as ground loop
Non is nothing more than a hum that occurs in particular situations especially when connecting grounded audio devices to each other. This inconvenience is most frequent in the case of connections with unbalanced cables (an unbalanced cable has only one conductor, also known as a hot pole, plus ground, while a balanced cable has two conductors plus ground), poor quality cables and is created when the voltage with respect to ground of the source unit ( A ) is different from the target unit ( B ) creating a potential difference and thus a current flow. Moreover, this problem becomes more pronounced when using an amplifier unit. By connecting two devices ( A - B ) with an audio cable, these two points are joined together via the braid (ground), thus forming a loop. This loop acts like an antenna by picking up electromagnetic noise in the surrounding environment or from the PC, which is amplified and reproduced together with the audio signal.
One solution to reduce or eliminate the ground loop is to use the floating ground (ground lift). The ground lift button used in many professional audio devices opens the connection between the device's grounding and the cable's grounding, preventing the flow of current along the shielding but maintaining the independent grounding of the individual devices.
There are also ground insulators (ground loop breaker) that contain a pair of audio transformers capable of isolating the masses of the two devices, thus preventing the ring from forming.
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