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
Sean, thanx, but what I was really wanting to know was at what distance, of separation of the wires, eliminates inductance and capacitance effects entirely? And if the shield is not used to carry signal, but only drains, does any impedance effect on the shield affect the sound? I expect that power levels will influence the distance, but what would you consider a "safe" distance apart, regardless of convenience? Also, would having separate + and - wires with individual shields/drains affect the spacing issue?
Twl, just running a "drain" aka "floating or telescoping ground" will alter impedance. I would therefore "assume" that putting ferrite over that would also alter it further. That is, at least within that small region where the ferrite was applied. After all, that what ferrite does. It creates an impedance "bump" within the nearfield.

As to specific ratios in terms of spacing vs capacitance / inductance, frequency and power levels, you've got the wrong guy. Better find someone that is both an EE and knows their physics : ) I'm WAY out of my league on stuff like that. Sean
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