How essential is shielding?

I just replaced a shielded PC with a non-shielded one on my preamp and the difference was dramatically positive. I'll be trying non-shielded on the mono blocks next and hoping to hear more improvement.

Cardas has a youtube discussion on this topic stating otherwise:

http://www.youtube.com/watch?v=9uhobsHs-_o

My theory is that if you stay below a certain price point (lets just say $500) then you just have to experiment with both typologies and pick your poison. As you get over say $1000 and up you start getting the best of both worlds. Of course there's plenty of snake oil that needs to be avoided but there are some real science behind a few of the higher end cables.

A comment on the Cardas video linked to above. I don't disagree with anything that was said, but I would point out that the main reason for the dramatic changes in the waveform displayed on the oscilloscope as the cable was moved about is that the other end of the cable was not connected to anything. If it had been connected to the output of a component, the output impedance of the component, being vastly lower than the only impedance that was present in the setup (the input impedance of the scope), would have made it a completely different story.

Regards,
-- Al

Almarg states the reality of cable choice. Location is paramount. I do use the Speltz ICs because they keep up with all the improvements I otherwise make to my system.

What do you guys mean by "dead quiet"?

Niacin - I mean (1) With the system turned on and no music playing, with the preamp volume in the maximum position I ever make use of, no noise is audible at the listening position; and (2) With the system playing music at my average listening volumes, with a good recording, during moments of silence between passages, the system sounds indistinguishable from being off.

4est and Elizabeth - You make a good point about shielding being more important in some environments than others. I've just been wondering if those environments are not as ubiquitous as manufacturers of exclusively shielded cables would lead us to believe, which brings me to...

Lokie - That Cardas video was exactly one of the examples I had in mind of a manufacturer advocating the exclusive use of shielded designs.

Al - Thanks for your excellent input. I looked at the linked paper, and I have a stupid question. Here's a passage from the paper:

To eliminate hum, we must effectively eliminate interchassis ground current. We could eliminate it by simply breaking the chassis to chassis shield connection. Of course, this alone would not solve our problem.

Here's the stupid question: Why? What would happen if you "simply [broke] the chassis to chassis shield connection" in an effort to eliminate interchassis ground current?

Thanks,
Bryon

Here's the stupid question: ... What would happen if you "simply [broke] the chassis to chassis shield connection" in an effort to eliminate interchassis ground current?

Hi Bryon,

That isn't a stupid question. The answer is that you would also be breaking the signal return path. Keep in mind that electricity only flows if there is a complete circuit, from source to destination and back.

If you were to break that return path in the interconnect cable, and both components had 3-prong power plugs, the return path that would be taken would be through the ac safety ground wiring of the power cords, and whatever additional safety ground wiring would be necessary to reach a ground point that is common to both components. That would result in noise problems.

If either or both of the components had a 2-prong power plug, and no other ground path existed in the system between the components, then the destination component would see a "floating" input voltage (i.e., one that is not referenced to its own ground). That would result in uncontrolled behavior, and very conceivably in full-power noise levels that could damage the speakers.

Best regards,
-- Al