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Old 13-02-2006, 13:28
fylor
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Forgive a dopy question but what are the ferrite things that are sometimes supplied to clip around cables? They never seem to make any difference but what are they supposed to do.
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Old 13-02-2006, 13:43
chrisjr
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They are used to suppress interference in whatever cable they are attached to.

For example a dirty or worn heating thermostat when it switches off can induce a great deal of noise into the mains wiring. This takes the form of very short duration spikes in voltage.

A ferrite ring changes the inductance of the cable which has the effect of making it more difficult for it to pass these short duration spikes. So they get removed to a certain extent reducing the potential for them to disrupt, say, the sound or picture in your TV/HiFi/Freeview/Satellite system.
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Old 13-02-2006, 17:49
fylor
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Thanks for that. So they are normally fitted on speaker cables or for example a mains cable to a plasma screen?
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Old 15-02-2006, 09:46
chrisjr
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Originally Posted by fylor
Thanks for that. So they are normally fitted on speaker cables or for example a mains cable to a plasma screen?
Unusual for them to be fitted to speaker cables. Mains cables are much more likely. Often they are an integral part of the cable, you may have seen cables with odd bulges near one end for example.

Mainly they would be used on signals going INTO a device. For instance the phono lead between a CD player and amp in a HiFi system. Putting them on speaker leads is a tad pointless as any "damage" to the sound by an interferance spike has already been done by it passing through the amp circuits.
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Old 15-02-2006, 18:51
mikeydb
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They can be fitted to speaker cables, but it's unusual unless you're finding the speaker cables are acting like a big antenna which can happen if you live in an area where local sources of rf cause a problem with your hi-fi.
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