| Paul R Johnson |
July 18th, 2009 09:32 AM |
Some countries have very stringent regulations on noise emmisions, like the UK - the problem with modern kit especially kit with switch mode power supplies is that they generate lots of 'interference' style noise, which often gets carried by the cabling into other pieces of kit. On top of this, most stuff nowadays have plastic cases. Some, like laptops, have an internal lightweight metal screen, but some don't bother. If you live near something with high output radio frequencies in use (I live next to a fire station), then the interconnecting cables can act as a sort of antenna, allowing the Radio Frequency energy into your system. I suffered from this in my edit suit, with the fire calls being heard at low level through the monitors. These ferrite filters, which simply have a loop of your cable passed through them allow low frequencies to pass through unaffected, but any higher frequency energy gets blocked by the filter. In my case, nearly, but not quite curing my problem. I've found them pretty useful on the power supply to my Dell laptop when I use it to feed a PA system. There is a large amount of background noise when the latop runs on mains power, but adding a ferrite ring removes most of this. If you have a bigger problem, then the magnet inside an old loudspeaker works pretty well too - just pass the cable through it half a dozen times, and then tape it up.
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