Why Expensive power Cables when Romex behind Wall?

Audioengr. I knew you would reply! That's why I mentioned the steel or brass outlet cover. Its a sure fire way to prove mechanical resonance. Come on man, go get yourself a steel or brass outlet cover - they are cheap 2 or 3 bucks. Replace the cover you currently use with it and then let us know what you hear. Before you write this off as snake-oil you ought to experience what other people are hearing.

Here are quotes from Audioengr's "Technical Papers" - seems he is contradicting himself in claiming that resonance is for the most part not audible - and discounting it as snake-oil here on Audiogon.

Conclusions:
Resonance is a very real behavior in most speaker cables. The nature of the speaker load will vary both the amplitude and frequency of the resonance. The fundamental resonant frequency is primarily a function of the cable length, but
different loads can move this frequency. Resonances can become a problem if high-bandwidth amplifiers are driving high-impedance speaker loads.

Empirical Audio takes resonance seriously, so we design anti-resonant terminations into our cables to eliminate the problem. We believe that the audible "Haze" or "Veils" that often overlay music in high-end systems is in part a result of cable resonance.

What he fails to mention is that there is no such thing as no resonance. Everything resonates. His "Anti-Resonant" terminations just change the frequencies at which the cable resonantes hence making it sound different - Did someone say SNAKE-OIL?

Empirical Audio has taken steps to deal with resonance in our cables. We put anti-resonant terminations in our cables to reduce this effect. To understand the effect of the anti-resonant termination, we first examine a cable without the termination.

Hmmm... so this confirms, you don't remove the resonance (you couldn't anyway) - you just change it. Isn't that what I said in my earlier post? -- Changing the resonant frequencies is one way that different cables sound different.

Bwhite's comments may be describing some of the differences I hear with premium power cables.

Nikkidanjo may be onto something where he describes cable shielding:

"Shielding the cables as they near this big rack of electronics may make all the difference. Perhaps the worst dirt is the dirt generated by your own system feeding back into itself. This could explain why shielding may help."

It may be a long wait before technology is developed that "proves" how some power cords work in our systems. Having heard significant improvements with several power cables, I don't intend to wait for a piece of paper telling me what I already know is true.

I have not tried metal outlet plates as Bwhite describes. I would not prejudge it effectiveness, until and UNLESS I tried it for myself.

I would likely believe in Mr. White conclusion, even if it failed to improve my system. Every system is different and it would be foolish to pass up an opportunity that at least one member has been successful with, especially one that costs about what some of us spend on a large soft drink.

I intend to purchase a couple of plates next time I visit Home Depot. Worse case I return them a few weeks later.

Thanks Albertporter! Please - don't expect the plates to make an improvement. They will however add a noticable and somewhat annoying brightness to your system. Hopefully this will help folks understand how mechanical resonance can play a significant role in what we hear in our systems.

Also, while you're at it, and if you feel like playing... the tightness of the screws which hold the outlet to the wall make a change as well.

After trying this with several outlet covers I ultimately decided to leave them off all together in my system. Having no outlet cover so far seems better than any other material.

Now if I can just figure out how to firm up that giggly junction box in the wall without tearing my sheetrock to bits.

Bwhite wrote:
"Here are quotes from Audioengr's "Technical Papers" - seems he is contradicting himself in claiming that resonance is for the most part not audible"

No contradiction. If you take the time to read the paper, you will see that I am talking about ELECTRICAL resonance, not mechanical resonance. I have extensive measurement and simulation data on this effect proving that it is real.

Mechanical resonance is a second-order effect at best. Electrical resonance is more of a first-order effect.

As for your metal outlet covers, I beleive that you are experiencing the placebo effect. There is no scientific explanation as to why this should make any difference whatsoever. Resonance requires a high-Q system, which this is not. Even if the outlet cover resonated, what electrical effect could this possibly have?

Nikkidanjo wrote:
"Basically, I don’t by the filter part unless some form of RF filter was deliberately added."

Agree 100%, power cords should not be filters, particularly on power amps.

The best analogy is that the pressure in the outlet of the pipe is the indicator of performance. If the pipe is 2" diameter for 25 feet and the last 6 feet are 6" in diameter, this will yield a much higher pressure at the outlet than if the pipe were 2" diameter the whole length. This is what happens when you add a low-inductance 6 foot cord to a 25 foot high-inductance wire in the wall. It really does work.