Why Expensive power Cables when Romex behind Wall?

No flames--I read a post in the Asylum by Jon Risch where he says he suspects 50% of the sound in power cords is due to proper grip...

For fun, do a little experiment, buy an inexpensive steel or brass outlet cover and install it in place of your plastic outlet covers. Plug in your system and listen.

You should notice a big change in sound.

WHY?

I will spit this out for discussion.

We cannot cure world hunger & explain every improvement we hear in audio as a direct result of decreasing capacitance and inductance while ensuring a low dielectric absorption. While this is important and the common angle to view how cables effect a system it is but a small piece of the puzzle.

Since everything resonates at certain frequencies, the wire (yes, the stuff inside our walls interconnects, and power cables) will resonate too. This is called (drum roll please...) Mechanical resonance. Mechanical resonance is particularly evident when energy is applied to something. Bang that drum again.... did you hear something?

While inductance and capacitance are very important in cable design and lets not forget dielectric.... Mechanical resonance is to a great degree what we hear when we hear differences in cables (and components). With power applied to the cable, it will resonate and thus emphasize certain frequencies, audibly changing the tonal quality you hear.

Cable geometry, and material used are key in producing neato sounding cables since they can effect the frequencies which resonate and those that don't. Different conductors will all resonate differently. For example: Copper resonates at 26.530MHz, Gold at 1.729MHz, Silver at 4.046MHz, and Platinum at 21.499MHz

The effects of the resonance of the material depends on the gauge of the wire and of course whether or not it is in contact with a sound deadening substance like Teflon - rubber - Shunyata Sand ... Virtual Dynamics Iron Powder or whatever. These substrates weight down the resonance to create the sonic signature.

Make sense?

Okay how about saying it like this:

Power coming into your house is already resonating - when you plug your cool aftermarket power cord into the wall, how do you think this could effect the sound? If the cable changes the existing mechanical resonance, it will change the way your system sounds.

So when you change your electrical outlet cover to a brass or steel cover and plug in your hefty power cord, you will hear a new mechanical resonance in your system and better understand as the topic of this thread reads -- WHY EXPENSIVE CABLES WHEN ROMEX BEHIND WALL... :)

Outlet quality and contact resistance is at least as important as the inductance of the power cord itself. Silver-plated brass outlets can work wonders for dynamics and detail.

Back to the question of the last 6 feet. Here are some calculations that I did to demonstrate the effect of a good 6-foot power cord:

A typical 6-foot 14 AWG rubber cord and 25 feet of ROMEX has inductance of 7.2 uH and resistance of 235 mohms, ignoring the plug resistance effect. Therefore, the voltage drop at 20kHz will be I*(wL+R)= I*(.905+.235) = I*(1.14). With a 6-foot Magnum2 and 25 feet of ROMEX, the inductance is 5.9 uH and the total resistance is 147 mohms. This is an 18% reduction in inductance and a 37% reduction in resistance. The voltage drop for this combination will be I(wL+R) = I(.741+.147) = I(.888). So at a fixed dynamic current I, the voltage drop in the entire power feed at 20kHz is 22% smaller with a Magnum2 power cord. I would consider 22% to be significant. The reality is even more compelling. When you add in lower plug and receptacle resistance and the fact that the di/dt on the power cord will have spectra well above 20kHz with some amplifiers, the low-inductance cord makes an even bigger difference.

Bwhite wrote:
"Make sense?"

Not to me. In fact, IMO mechanical resonances account for very little that is audible in most systems. Certainly if you put your components on a thin steel shelving unit, you might get some mechanical resonance effects, but most systems do not experience this. If anything, the electrical resonance of longer cables has a more pronounced effect. You are taking the snake-oil literature out there too seriously. Here are some papers that are not snake-oil:
Technical Papers and Audio FAQ at:
http://www.empiricalaudio.com

OK I’m an electrical engineer who has never tried to play with power cords. This means I know just enough to be dangerous but not enough to really know what I’m talking about. I am not going to claim that power cords do not make a difference because I suspect they do. That said, here’s my 2 cents.

Electrical power cord as filter: I’m not convinced but… The parallel is a fuel or water filter. Water travels for miles in dirty pipes but the filter at the end is able to clean it up. This argument does not work with power cords. A power cord is the last section of pipe, not a filter at the end. As such the analogy would be miles of dirty pipe with a clean section at the end. Not adding dirt for the last few feet isn’t going to help. A power conditioner is a good analogy to the water filter. IF the power cord has some form of filtering built in, that would be different. A power cord might include a high frequency filter to clean RF noise or something. Even if the designer didn’t intend it, the geometry of the wire could make a filter of some sort (I wouldn’t put money on it). Basically, I don’t by the filter part unless some form of RF filter was deliberately added.

Electrical power cord as the last few feet of pipe: Using the water analogy
1. The original pipe was too small (ie wire gauge too small). If the power cord was too small to handle the current you could get voltage drops. My 240wpc Bryston amp came with a heavier power cord than my Bryston preamp. Thanks to V=IR loading on the power lines and cord the amp might see a significant reduction in line voltage. I would expect this to hurt amplifier performance. If your system is plugged into a power strip this voltage drop might be shared with the other components in your system.
2. The pipe has flashing around the fittings (ie the plugs don’t mate well). Maybe the issue isn’t the last few feet but the connections at the plug. Just like the issue with small gauge wire, a bad connection can cause a voltage drop. This would explain why high quality hospital plugs can make a difference.
3. The last few feet of pipe is where all the dirt is! Perhaps the power from the wall isn’t that dirty but all your equipment is really making the noise. 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.

Take it for what it’s worth. Personally I think cables make some difference but I would rather spend the big money on components rather than cables.