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<blockquote data-quote="stones" data-source="post: 1388600" data-attributes="member: 540734">When two or more devices are connected to a common ground through different paths, ground path noise, or a ground loop can occur.&nbsp; Thus, a system grounded at two different points, with a potential difference between the two grounds can cause unwanted noise voltage in the circuit paths.&nbsp; Currents flow through these multiple paths and develop voltages which can cause damage, noise or 50Hz/60Hz hum ( variable in cars due to alternator rpm )in audio or video equipment. The ground loop can be eliminated in one of two ways:1)&nbsp; &nbsp; &nbsp;&nbsp; Remove one of the ground paths, thus converting the system to a single point ground.2)&nbsp; &nbsp; &nbsp;&nbsp; Isolate one of the ground paths with an isolation transformer, common mode choke, optical coupler, balanced circuitry, or frequency selective grounding.The most practical and usually most cost effective method for consumer audio applications is to use an isolation transformer.&nbsp; An isolation transformer is a device which, in the case of cable signals, allows all the desired signals to pass freely, while interrupting ground continuity, hence breaking ground loops.&nbsp; By using an isolation transformer, the ground noise voltage will now appear between the transformer windings and not circuit input.&nbsp; The noise coupling is primarily a function of parasitic capacitance between the transformer windings and can be reduced by placing a shield between the windings.&nbsp; This is an effective method to implement assuming the transformer has sufficient bandwidth, isn’t too costly or bulky, and a direct DC signal path is not required for the application.</blockquote>

[QUOTE="stones, post: 1388600, member: 540734"] When two or more devices are connected to a common ground through different paths, ground path noise, or a ground loop can occur. Thus, a system grounded at two different points, with a potential difference between the two grounds can cause unwanted noise voltage in the circuit paths. Currents flow through these multiple paths and develop voltages which can cause damage, noise or 50Hz/60Hz hum ( variable in cars due to alternator rpm )in audio or video equipment. The ground loop can be eliminated in one of two ways: 1) Remove one of the ground paths, thus converting the system to a single point ground. 2) Isolate one of the ground paths with an isolation transformer, common mode choke, optical coupler, balanced circuitry, or frequency selective grounding. The most practical and usually most cost effective method for consumer audio applications is to use an isolation transformer. An isolation transformer is a device which, in the case of cable signals, allows all the desired signals to pass freely, while interrupting ground continuity, hence breaking ground loops. By using an isolation transformer, the ground noise voltage will now appear between the transformer windings and not circuit input. The noise coupling is primarily a function of parasitic capacitance between the transformer windings and can be reduced by placing a shield between the windings. This is an effective method to implement assuming the transformer has sufficient bandwidth, isn’t too costly or bulky, and a direct DC signal path is not required for the application. [/QUOTE]

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