Sheilded/Unsheilded Power Cords

Audioengr: Sorry to step on your toes, but thanks for proving my point. Your line of questioning to Marty just goes to show that even those that i consider to be "worthy" and design / manufacture PC's think of them as nothing more than "an extension cord" ( hypothetically speaking ).

While you have a point about what happens upstream from the PC, you also have to take into account several other factors:

1) One can piss anywhere along the river that they want. So long as the contents of the river are highly filtered prior to delivery to the water fountain, i don't care what takes place. In effect, one could use unshielded wire for a few million miles. This would in no way reduce the effectiveness of a well designed filter at the end of the wire.

2) Why is it that most engineers / designers / manufacturers have such a hard time thinking of a power cord as being anything more than a "conduit for power delivery" ? Aren't the internals of a PLC made up of capacitors, inductors ( which is nothing more than wire or wire on a former), resistors, diodes, impedance altering devices, etc.. ??? What would stop someone from applying filter technology and the associated componentry to a power cord design ?

3) The fields generated by the in-wall wiring are not anywhere near as close to the low level signal carrying cables and components as the power cords are. Therefore, EMI and radiation from the in-wall wiring is far less critical.

4) Stop thinking of a power cord as an extension cord and start thinking of it as a part of the power supply.

Sonic Genius: Your comments apply only to designs that are made by those "thinking within the box". If you were to step outside of the "box", you might begin to see how those factors could be reduced or even put to use as a positive aspect of the design. Certain design attributes are only "negative" when you can't control them or they are not taken into account for. When it comes to AC, signal manipulation is the name of the game. Sean
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On the flip side the "dynamics" seemed improved with the shielded DIY's. The highs seem higher and the lows seem fuller. Interesting...

This may be true, but it is difficult to attribute this to the shielding. The new cables were likely lower capacitance or lower inductance as well.

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

Yes, but it also contributes to a low-pass filtering effect when installed in the system. Creates an impedance to high-frequency currents.

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.

It seems to quack and look like a duck....

Sean - No offense taken.

Why is it that most engineers / designers / manufacturers have such a hard time thinking of a power cord as being anything more than a "conduit for power delivery"

I can only speak for myself. A power cord is just one segment of a longer power transmission circuit, which can be described as series resistance and inductance and parallel capacitance. However, the catch is whether this is described as a lumped parasitic or a distributed set of parasitics, like a transmission-line. The former is used at low frequency and the latter at high-frequency. The debate goes on ...

Aren't the internals of a PLC made up of capacitors, inductors (which is nothing more than wire or wire on a former), resistors, diodes, impedance altering devices, etc.. ??? What would stop someone from applying filter technology and the associated componentry to a power cord design ?

Nothing. You can get filtering effects from different power cord constructions or just add filtering elements to the cord, such as inductors, ferrites, resistors and caps.. I do not happen to believe in filtering in PC's myself, except for the ground wire. This can be useful to minimize noise from ground-loops.

Stop thinking of a power cord as an extension cord and start thinking of it as a part of the power supply.

I agree. Certainly is a part of the power system. As is the transformer on the pole and the transmission lines that deliver to that. However, the further that you get from the component, the effects of the component load on the system become smaller and smaller because the impedance of the source gets increasingly lower. At some point, you ignore the effects because they are second-order. I have chosen this point to the be power panel in the house. This causes a small error in any calculations of power delivery.

Radiated power drops rapidly with distance. No need to shield Romex in wall. It's too far away from the system.

The power cord, which is the last 6' of the power delivery system, seems to be an ideal place to put a tuned filter. Filtering out everything but the pure 60Hz using a power conditioner and a tuned power cord would seem to be optimal.

It seems that shielding on a power cable would keep it from radiating noise to the high impedance lines, such as the IC's. If the power has high frequency noise, it may radiate this too. Shielding is a difficult design process, however. No doubt many manufacturers just use trial and error.

Just my 2 cents (or maybe 3).

Sean - as usual, right on the money! I especially like what you said about thinking outside the box.

Those of us who have built AC power cords realize that it is quite difficult to make sonic improvements beyond a certain level - which isn't all that fantastic in the grand scheme of available audiophile AC cords. Cables which carry low level signals are easier to improve upon.

Why do we suppose this is? Come on guys, think outside the box!!!

AC cable manufacturers like Electraglide, Elrod, and Shunyata for instance, have thought outside the box. It is doubtful that any of these cables measure well from an "inside the box" mentality yet the results these cables bring to a system is dramatic - far exceeding anything *I* have ever used from an "inside the box" kinda manufacturer or DIY enthusiast - at any price.

Regarding 'electronic add ons' to power cords. I seem to remember Bob Crump post that he fiddled with making a power cord for years without the ability to make any real improvement in sound from a stock cord....until he finally decided to add some circuitry to the design and hence make the improvements he was after.

Now... If Bob Crump cannot make a significant sonic difference with "inside the box" thinking it is doubtful that anyone can and I don't care who they are!

So those of you who believe in measurement and inside the box thinking as it applies to audio (especially you Audioengr). I dare you to find a Power cord that measures well and lets put it up against an Elrod Signature cord, Electraglide FatMan K, or Shunyata Anaconda Vx. I'm sure all three of these cords measure differently and all worse than an "ideal" cord... yet, I guarantee they will absolutely blow the doors off anything which measures good.