Sheilded/Unsheilded Power Cords

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.

Honestly, when I was done braiding the wire and all the mess, the DIY were going to be better...No matter what :).

I had not a/b the cables, until just before this reply. "more noise" between the two- nope. Seems to be the same. I had meant this for another post, how much noise is too much? The old crank the volume and stick your ear up to the tweeter, I do here a little noise. Not heard from the listing position, but can hear with my ear on the tweeter. Not sure really how to put this into words. The tuner will bleed into the next/nearest analog input. $6000 bucks for bleeding inputs, huh.

On the flip side the "dynamics" seemed improved with the shielded DIY's. The highs seem higher and the lows seem fuller. Interesting...

The amp circuit to the wall is unshielded, all runs in the room are shielded. The source circuit is actually shielded all the way to the breaker panel. I use balanced ic where possible, from the processor to the amp. With HT, one seems to have a few more devices, which seem to add more possible problems.

No, the existing ROMEX are not shielded. That's the reason a normal person would buy the live lead finder pen(I gotta find out this thing is really called), to find these lines. My equipment is also not placed directly up against a wall, next to these lines.

Please explain what "unwanted capacitance" means. Is this the ability of the wire to store a charge.

Also the power conditioners in the system are a ps ultimate outlet ran into a Richard Gray 400. Really weird part with out the power conditioners, the buzz is 75% louder, plain as day. What I would call very bad. With the ps, same. With the "noisy" RGPS, very quiet. Funny, exactly the opposite of what I would have thought.

I hope I am not describing a long winded minor ground loop hum. This was not the purpose of the thread. This background noise is very minor.

Learning something new every day,

Thanks all
Marty