12 Faultfinding Your System
Cause and
Elimination
of Hum
Hum is a particularly annoying form of noise in any high fidelity system and at some time has been experienced by many of us.
Hum may result from a number of different situations and to make matters worse maybe caused by a seemingly illogical combination of circumstances.
One or more of three specific causes creates hum in the system.
Induced Hum
Hum can be induced into the system from one or more sources and is generally associated with the radiation of noise from one system into another.
Hum and noise can be radiated from any object or system involving AC voltage and current such as power supplies in amplifiers, motors, switching equipment etc. All of these may be found in your
Hum may be induced into any part of the system, so there are no specific instructions that can be given which will offer a guaranteed cure. A good practice to adopt is to keep
The practice of neatly tying excess leads together for a tidy looking installation should be resisted, as this could be the cause of induced hum in the system.
Earth Loops
Earth loops are a particularly annoying cause of hum in the system. Earth loops are created by mains frequency current flowing in the screen of signal leads and becomes apparent with the lack of adequate earthing between the various pieces of equipment making up the
Perreaux products used with equipment manufactured by other manufacturers may cause an earth loop situation, but Perreaux products used with other Perreaux products will not cause an earth loop situation provided the following precautions are observed:
The entire
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