Use of Ferrite Cores for EMI Reduction???


I've been doing a lot of research on the net lately about the use of Ferrite Cores to reduce ElectroMagnetic Interference (Yes, I are an engineer). It started when I bought a digital camera and there was a Ferrite Core at each end of the USB Cable AND one at the end of the power supply going into the Camera. The directions said that it was for noise reduction through those 2 cables! So I thought, HEY, I have cables in my Audio System...

This really got me thinking about the use of Ferrite Cores to significantly reduce the influence of any stray EMI that could be degrading the sound quality. Does anyone have an idea of this would help, OR does the EM shielding that already comes with most cables do the trick?

Any hardcore Electrical Engineering input would be GREATLY appreciated. Am I on to something worth trying, or just full of bunk??
hager_charles
Charles, the use of ferrite is pretty widespread in various electronic fields. There are many in's and out's as to where it can and should be used. The one main drawback to use of ferrite's has to do with saturation. Knowing the magnetic properties of the specific ferrite being used can come in handy. As such, you might want to experiment with use of ferrites on various cabling. Some manufacturers already include beads or clamps on some of their products.

I would not go crazy with quantities and pay attention to where you place them at. I would also mention that their use on power cords for high current items ( like power amps ) are more questionable than anywhere else, so keep that in mind. Sean
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Commercial products you might want to consider are Audioquest's RF Stoppers and RF Stoppers, Jr. Radio Shack also sells ferrite cores appropriate for audio systems. I was getting RF noise through my turntable, and using three (one on each phono interconnect plus one on the power cord) of AQ's RF Stoppers worked well. Admittedly, the core on the power cord theoretically shouldn't make any difference since there is no conducting path between the motor and the tonearm; I used a core anyhow to minimize any rebroadcast interaction possibility (the AQ's came in a pack of four).
Hi,
If you want to experiment, I believe that Audioquest sells cores in two sizes for use on power and interconnect cables. I think they are called RF Stoppers or something similar. They are relatively cheap and come in simple snap on cases. I have them on my power cables to everything but in truth I never A/B'd to see if there was a difference. I think Stereophile gave them a thumbs up in their accesories category.
Phil
You can buy a "billion" ferrite clamps in various sizes from either Digi-Key or Mouser ( can't remember which ) for the price of one small package of the Audioquest stuff.

Do a search through the old Greg Weaver articles on Soundstage and he even gives you part numbers. Some of these might not be valid anymore, but the dealer can probably cross reference them to current stock. They do have a minimum order, but it would still be less than buying a package of the AQ parts. If you can't find the part numbers, i'll try to look them up tonight or tomorrow. Sean
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Hello Charles. Have you visited this website? It has a very good discussion of noise and ways to control it. Also a *very* good DIY noise control section:

http://www.magnan.com/