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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

Showing 2 responses by bob_bundus

bob_bundus
1,834 posts
 
be careful what you do with those ferrite clamps. I clamped 1ea. on a pair of Audioquest Lapis interconnects; they killed the highs & PRaT was all but gone. Sold the whole pack forthwith.
bob_bundus
1,834 posts
 
Those RF Stoppers were used on a much different rig than my present setup. I was having a lot of RFI problems from trucks on a nearby highway; I'm surprised that my amp or speakers didn't blow up when some of those clowns went by with their (non)linear amps broadcasting simultaneously on all 40 channels. Their $hi! was supersaturating an older preamp, then of course the hash was amplified by my PA. I put those RF stoppers on the analog interconnects driving the PA; I clamped them on the cables within a few inches of the amp. The RFI was indeed substantially reduced to the point of being tolerable, but they just ruined the sound, & these were just the 'junior model' RF Stoppers. They do have spacers on the inner diameters of the clamps in order to help avoid the aforementioned assymetrical positioning problem. I used some electrical tape for that purpose but I do like the wrapped-paper idea because then the clamp can be moved up or down the cable for positional optimizating.
I've seen ferrite cores installed on power supply cables & AC cords (the Audioquest AC12) which maybe makes a little more sense, but when used on analog interconnects they were awful.
Respected designer Charles Hansen (of Ayre Acoustics) actually told me that when Ayre was experimenting with ferrite AC filtering, they found that the initially realized improvements were degrading over the long term due to a "magnetic buildup" within the cores, which had to be degaussed periodically. He also mentioned that ferrite was causing some sort of 'grunge effect' on the sound, another reason that they didn't like it.
Francisco thx for the Powerwrap report; I need to order one to play with but I'm hoping to find an alternate source vs. the near-north retailer that sells them in our area. I still have a bad taste in my mouth leftover from my latest dealing there; it's not a BFD but next time I'm going elsewhere if possible. Does the package show the manufacturer's name & address? Please advise if you have this info? thx
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