Can Power Cords Have an Effect on an Audio System's Sound?

Cable discussions can turn normally rational audiophiles into nut-cases. I know. I've been reading and watching the discussions since I wired up my first stereo system.

AR-pwrcord1acopy.jpgRecently I decided to ask two industry participants their take on power cords. My question was, "How can a basic stock AC power cable negatively affect audio gear?" 

Here are two divergent viewpoints...

From Tommy O'Brien, Digital Amplifier Company

"The most important feature of a power cord for amplifiers is simple resistance. Other factors such as capacitance, inductance, and shielding, are "in the noise" and not significant enough to affect the sound of even the most revealing audio systems.

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For power amps as well as other equipment, the quality of the connectors is important, but the reasons are reliability and contact resistance. Good quality is a must for any decent system, with every part of the system. Decent quality doesn't mean high price.

It's important to mention that well designed equipment doesn't need special power cords or even power conditioning. Well-designed equipment filters and regulates power internally so that, aside from brownouts or blackouts, the equipment runs flawlessly even on distorted and noisy AC power. Going "off the grid" is another unnecessary endeavor with good equipment, as far as sound quality is concerned.

AR-CHerry amp2a.jpgAnother fact regarding power cords is that, behind the wall, there are 10's of feet (sometimes more) of household wiring to the breaker box. If people think beefing up the last 10% of 60 foot run is going to make a difference, they will be sadly mistaken. Therefore, spending more than $100 on a power cord is usually a waste of money."

From David Salz, WireWorld Cable

"Generic power cords actually do cause audible problems and that's why a thoroughly engineered cord can make great improvements in music reproduction. Of course, the reason we hear sonic changes from power cords is that component power supplies are imperfect and they allow power line noise to mix with the music, which masks detail, adds coloration and compresses the sound. Shielding a cord is helpful because it can eliminate external interference and increase capacitive filtering, but other audible problems remain. These problems include triboelectric noise, strand interaction and contact noise.  

AR-DNA Helix1a.pngTriboelectric noise is a static charge/discharge effect that takes place where conductors touch insulation. This noise is commonly defined as a reaction to vibration, but we've found that it is also generated by the current passing through the cord. The magnitude and frequency distribution of this noise varies dramatically according to the insulation materials used in the cord. The standard PVC insulation used in generic cords is not quiet. 

The conductors in generic power cords are bundles of bare strands, which cause the audible problem known as strand interaction. Simply stated, strand interaction is caused by the electromagnetic proximity effect, which forces some of the current to jump from strand to strand as it passes through the cord. Of course, the connections between strands are imperfect and often poor because the copper oxide on their surfaces is semi-conductive, so it also creates noise. 

AR-metalconductivity1a.pngThe plug contacts on generic power cords also create noise. In particular, the common nickel plated brass contacts are especially noisy because of their low conductivity, but bare brass can even be worse if it's corroded. Improving these connections alone can make dramatic improvements in sound quality and silver contacts are measurably quieter than the alternative metals."

So how do I, a reasonably intelligent audiophile, respond to these two divergent points of view?

My paraphrase Mr. O'Brien's thoughts are "Well-designed gear doesn't need a premium power cord priced over $100 because it has circuitry inside that can reject AC power noise."

My paraphrase of Mr. Salz is, "There are three primary sources or AC noise and inexpensive and "standard" power cords do not address any of these noise issues."

AR-pwrcord2a.jpgSo, what can an audiophile do after reading such differing opinions on a similar subject? For me the answer has always been "try listening yourself." If I hear a consistent improvement by inserting (or removing) something from the signal chain, I can only conclude that there is a reason for using something different from a stock AC power cord. All you need for a test like this is two consenting audiophiles - one to listen and the other to do the switching...

Let me know how your tests work out...

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