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What are these things? they are on all my minidisc appliances

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It's a clamp filter with a ferrite core for absorption of high-frequency EMC (Electromagnetic charge?). The one you have is at least removable, on later models some are hard wired into remotes and power supplies. Simply annoying extra bulk. I'd remove it, but put it somewhere safe just in case...

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I always remove them. They only exist so Sony can say their products are not emitting any high frequency emissions, keeps the FCC in the US happy. Removal should have no adverse affect on the performance of the device. It is however that removal may cause interference with other devices, but not likely.

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The major places I've seen interference on signals (not necessarily from MD) are:

1. Analog TV (CRT and the like). I have had none of this since getting LCD a couple of years back

2. Hum from ground loops and the refrigerator. This is gone since we redid all the wiring, but it used to be a real problem. Whether the chokes worked, I don't know but they're probably not a bad idea.

Ever put a speaker too close to the back of a CRT (outside, of course)? Weird and wondrous onscreen colours, and you need to enter the monitor's degaussing routines.

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  • 5 months later...

Glad to know I'm not the only one who was stumped by them a while ago haha, I've seen them around before, and always wondered what they were and then I found out they were ferrite beads.

Like most of you have said, I can't see the point of them, I can imagine they make the smallest bit of difference, if at all. Most things these days are shielded against interference so they seem unnecessary.

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Actually, they are quite important in order that electromagnetic radiation is kept in check. With the proliferation of electronic devices, it is imperative that they do not interfere with each other. More specifically, that non-essential equipment does not have an adverse effect on essential installations. You know, important things like life-support equipment and avionics.

These filters are designed to reduce very- and ultra-high-frequency emissions which can easily cause interference. If we look at the minidisc recorder as an example, even those made from plastic parts include a degree of shielding using ground planes, metallised plastic guards and so on. However, it is not possible to protect the external cabling from EMI (electromagnetic interference).

Some may say 'ah yes but these cables only carry low frequency audio signals'. Not so. High frequency signals are always present due to inductive and capacitive effects. The control processors found in most modern electronics run at GHz, and clock and signal frequencies will always make their way ultimately onto external connections. The way around this is filtering HF signals, which can be done to some extent internally but is far easier (and cheaper) by adding filters to the cables - including the power cables as these digital clocking signals can also propagate back through the supply.

Hence the chunky filters around which the cable should be looped several times.

And of course the problem is cumulative. One badly shielded device may be ok, but a whole aircraft full of them and I for one would prefer not to fly in it, thank you. And I am sure bodies such as the FCC and the EU equivalent wouldn't spend millions/billions researching and implementing these requirements unless there was a definite need.


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