Use of Ferrite Cores for EMI Reduction???

Sean, please elaborate on your comment of high inductance characteristics for the cable I mentioned. I believe that as inductance increases with proximity, the 1/2 inch minimum separation of conductor to shield should be adequate to reduce inductance to a minimum. Larger separation would be better, but we must retain some level of ability to move the cable around. With the pos. and neg. each run separately in their own separate tubes, they would not interact with each other significantly. I am aware that inductance affects can be present from AC 120v power cables as far away as 1 foot, but in the smaller power levels present in interconnects I don't think the problem is anywhere near that magnitude. Also, I mentioned that I would prefer no shield, but was trying to address his RF splash problems.

Bringing conductors closer together moves them more towards being a capacitive load. Spacing them further apart makes them less capacitive and moves them more towards the inductive side of reactance.

When one can find equal amounts of capacitance and inductance at the same point, the reactance is effectively nulled. While this can be achieved, it typically varies with frequency. As frequency rises, wavelengths are shortened and the gap between conductors appears to widen. That is why zip cord is more inductive than a twisted pair given the same amount of insulation around each conductor. Both start out relatively even at very low frequencies but the gap between inductive reactance and capacitive reactance widens as frequency climbs.

The twisted pair has more intimate contact area between the two conductors as they spiral around each other. This increases capacitance / lowers inductance. The zip cord has only one continual point of contact along their lengths and is therefore more isolated from each other. As a result, inductance is increased and capacitance lowered.

As a side note, anyone that has tinkered with speaker crossovers knows that putting increased inductance in series with a speaker will roll off high frequency response. Hence, the lack of treble clarity and extension when using zip cord with thick insulation.

As one can tell, this is a very simplified example. If you want further proof, take some Goertz speaker cable and separate the conductors. Not only will it no longer be a high capacitance design, the total impedance will be drastically altered. Sean
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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?

Sean, in the above when i said impedance I meant to say inductance.

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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