Sheilded/Unsheilded Power Cords

Marty, your "DIY research" has exposed more "truths" than many manufacturers / engineers will ever come to realize in a lifetime. The reason for this is that you can't find the "hands-on" results that you experienced first hand in a text book sitting at a desk or bench. This is NOT a poke at Steve aka Audioengr but a generic comment. I hope that he understands this and does not take it personally. I know that Steve is working very hard to do the best he can and does so with both hands-on testing and using very high grade test equipment. Quite honestly, i know first-hand that Steve has more advanced test equipment than most of the other cable manufacturers out there and knows how to use it. I am not endorsing his products as i have never used them, but i don't doubt that they perform well based on REAL scientific research and listening tests. Sean
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David Blair at Custom Power Cord Co. in Skokie IL uses heavy liberal shielding for all of his AC cords with great results; evidence that this can in fact be done to good effect when properly engineered.
Now take another look at shielding from a somewhat radical perspective: specifically, the Synergistic Research "active shielding" approach. The applied DC voltage potential on their cable shields (which are out of the signal path) is said to saturate the insulation dielectric such that it won't leach electrons from the signal carrying conductors. I admit to healthy skepticism when I first read about this unique shielding system, & was still rather doubtful regarding its benefits when I first auditioned it with some decidedly mid-fi componentry. Yes I heard an improvement with the active shielding power supply energized, but not enough difference was perceived to justify the expense.
Later on, after significantly upgrading my rig to better quality components, I decided to incorporate the active shielding system. Now I could really hear a significant difference between the active shielding vs. passive shielding; this system really does work. Proof that this effect is not just psycho-acoustic came to me a few months later, when the rig was shut down during a storm. Wife had powered the system back on the following day, but had neglected to turn on the shielding power supply (they call it a Master Control Center - but it really doesn't control anything). I came home from work & even casual listening revealed a deficiency, but I couldn't quite quantify the actual problem. Bass was lacking, dynamics were softened, highs just weren't what they should be, staging was constricted. I suspected the disc that she was playing, until other more familiar material didn't measure up either. Sitting in the living room, I was gazing at the rack & then realized that the tiny blue LED AC power indicator for Master Control Center was not turned on. Turned on the power switch & everything fell right back into place. That's proof enough for me; I'm not "imagining" these effects.
Synergistic has since incorporated active shielding into their AC cords & even speaker cables. Currently, only my Synergistic interconnects have the active shielding, but I now plan to retrofit my AC cords. I don't use their speaker cable so I can't really comment on that; however I remain convinced.

Bob's not going to like this,

I wonder how one could do a DIY active shield? Put a dummy load on a small DC transformer and shoot the current up the shield, or wrap the wire around the cable?

I must say that with my limited, yes very limited tester, the shield and drain on the wire I used seems to work very well.

Thanks all,

Marty

I agree with audioengr, shielded power cords are unnecessary. The extra ground capacitance and dielectric distortion is undesirable.

Marty9876 wrote:

The field an unshielded pc gives off seems to be large, at least 12 inches.

The fields may be large depending on the construction of the power cord. Many cord designs are field-cancelling, and they are not shielded. I dont doubt the you measured larger fields with unshielded power cords, but what about the ROMEX in the wall? Did you shield that too? This ROMEX is usually substantially longer than the power cord.

Also, did you have more noise with the unshielded power cord than the shielded one?

The reason that I ask is because I have seen many audiophiles chase their tails trying to eliminate noise with shielding on IC's, power cords and even speaker cables when the problem turned-out to be a ground loop. Since your system is all single-ended, this is more likely. Using more than one circuit outlet to plug all of the components also increases the likelyhood of a ground-loop. Grounding and shielding is a non-trivial field of science. I have taken courses from industry "experts" in this field.