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RE: JSSG 360 Theory

Posted by Jon Risch (B) on October 24, 2020 at 09:13:35

In Reply to: DC Cable Comparisons posted by Jon L on October 10, 2020 at 19:53:54:

One's listening experience always tops any theoretical considerations.

We may not know exactly WHY a tweak works, but if it does result in better sound to a group of enthusiasts, and we can't seem to measure a difference, then we probably just don't know what to measure or where or how to measure to ascertain the differences.

That said, I wanted to comment on the JSSG 360 basics.

RE the JSSG Theory involving an extra wire to be connected at both ends of a cable shield for maximizing shielding, there appears to be some mistaken and/or conflicting information presented.

First, a classic Faraday cage or cable shield, no matter how it is connected, will not shield against a static (DC) EMI field.

Yet in John Swenson's post at computeraudiophile, he states:
"The best way for shielding to work properly is a separate wire connected to each end of the shield. This is sufficient for shielding from DC to very high frequencies."

The part about a Faraday cage shielding from a DC field is just plain wrong. Not going to be able to do anything about a DC field.

IF the added wire connected at each end is actually going to have a beneficial effect for AC fields, then it's effect will be limited to the bandwidth it can handle, what it can actually pass.
This simple single wire will become inductive relatively quickly as the frequency increases, thus it's effectiveness at radio frequencies (much less VHF) will be very poor, if there is even any significant conduction at all.

In order to maximize the loop shielding effect, then this "extra wire" would actually need to be another layer of coaxial shield insulated from the inner shield, and connected at both ends, etc. Then it might at least be able to operate up to some high frequency effectively.
Interestingly enough, this is usually how a triaxial coax cable is connected.

However, the very principal that a Faraday cage operates on does not depend on an additional conductive loop outside the cage, as the conductive material of the cage itself, if it is going to function as a Faraday cage, will be conductive, and the "loop" he refers to is occurring inside the conductor itself. If it did not, then there would be no Faraday cage shielding effect.

Is it possible that adding an encompassing layer of insulated conductor outside a single layer Faraday cage would add to the total shielding effect? It is entirely possible, as you have now "double-caged" the enclosed space.
Any leakage through the first box/cage would then be intercepted by the inner box/cage and further reduced.

To illustrate my point about the use of a second braided shield over the first one to complete the JSSG loop for increased effectiveness and a wider bandwidth, think in terms of a classic Faraday cage that had a single wire looped around the out side and connected at one side and then the other side of the cage. Is this going to be as effective as a complete second cage in boosting the shielding? Not likely.

So for those who like what the single wire does for their wiring/shielding situation, I suggest that you try a complete added braided shield over the first shield. Take a suitable cheap coaxial cable apart to use just the braid, most braids can be expanded some to go over larger diameter cables, you just have to allow for the shrinkage in terms of extra length of sacrificial cable you are using to provide the braid.
The connections can be of a hard connection type (direct soldered connection), or through an RF grade capacitor that would then tend to pass mostly RF frequencies, say a 0.1 uF cap or perhaps even a smaller one at 0.01 uF. Of course, a mix of a hard connect at one end, and a capacitor termination at the other is worth a try as well.

I also caution against letting the shield "float" without any type of ground at all, either it or the added conductor can then act as an antenna at certain frequencies, so grounding it at one end or the other, or through an RF grade capacitor at one end or the other, would certainly be something that should be tried, and as long as it did not noticeably degrade the sound, I would leave it in place for a future potential RF event to be controlled if needed.


Jon Risch

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