The best introduction I have ever read about power cables was written by Caelin Gabriel of Shunyata Research Inc. Although this is a Transparent Audio thread, it is general enough to be posted her.
Introduction: “There are a lot of misconceptions about power transmission and power quality that make it difficult for some people to understand why a power cord makes a sonic difference. The first question is – do power cords make any difference at all? There is no sense in talking about theories of operation if we can't agree that there is an audible effect. Most of the thousands of people that use our power cords started out as skeptics and have answered that question for themselves and have found that power cables a power conditioners can have a profound impact on performance. And no - I do not care to debate with people that have not done the simplest of tests about whether power cords work or not. The only cases where a high quality cord does not have significant effects is when it is used with a poor quality power conditioner that acts as a high impedance to instantaneous current flow. “
Misconception #1: AC Power is like water coming from a large power tank, flowing through several 10s of feet of power hose into a component. This implies that the component is at the end of this system.
Answer: “Actually, the component sits between two power conductors: the hot and the neutral. AC power oscillates (alternates) back and forth at a 50-60 Hz rate. So power does not pour into the component at all. The component's power supply is within a complex network of wires and connectors. ALL of the wire and connectors can and do affect the performance of the component's power supply.”
Misconception #2: AC power can be contaminated just like water in a hose. This implies that once the water is contaminated at some point up stream, that is must be cleansed before it arrives at the audio component.
Answer: “As stated in #1, the component is not at the end of the power hose. It is between two power hoses and the current is oscillating back and forth. Further, current is not like water at all. Electrons cannot be contaminated. There are two aspects to power transmission: the electromagnetic wave and the current flow. The current itself cannot be contaminated but the electromagnetic wave can be modulated with other frequencies. We usually call these other frequencies noise or Electromagnetic Interference (EMI). Within the various parts of a power circuit there may be EMI in certain parts that is not present in others. Electromagnetic energy can be transformed or redirected to lessen their effects.
Some power cords use capacitors, inductors, or ferrites in an attempt to control the electromagnetic fields around the audio component. The success of such an approach is completely dependent upon the specific design and the reactance of the power supply of the component to which the power cable is attached.”
Misconception #3: There is up to a hundred feet of wire in the walls, so the last 6 feet of power cord can't possibly make any difference.
Answer: “The power cord is not the last 6 feet, it is the first 6 feet from the perspective of the component. As stated in #1 the local current and electromagnetic effects directly affect the sonic performance of the component.”
Misconception #4: There is a tremendous amount of electrical interference and EMI coming from outside the home that we need to protect our equipment from. This implies that we need some sort of power conditioner or filter to protect the equipment.
Answer: “Most of the EMI that affects the audio quality of a system is generated by the audio components themselves. Electromagnetic waves that traveling through space dissipate in power at the square of the distance from the source. Further, very high frequencies that propagate through the power circuit do not survive for long. Power lines present a high impedance to MHz and GHz signals due to the relatively high inductance of power lines.
A primary source of audible sonic degradation is caused by the power supplies in our audio/video components. Most components use FWBR (full wave bridge rectifier) power supplies that generate an incredible amount of transient noise when the rectifiers switch off. The design of a power cable can significantly affect the reactance of these signals within the power supply. The power cable is effectively part of the primary winding of the power transformer. The transition between the various metals used in a power cable and it's connectors can cause electromagnetic reflections and diode-like rectification of the noise impulses as they propagate away from the power supply. If the power cable presents a high impedance to these signals they will be reflected back into the power supply where they will intermodulate, thus increasing the high frequency noise levels of the component. Most power supply filters are ineffective at blocking very high frequency noise components and much of it is passed through to the DC rails. The sonic effects of this include: high background noise levels, blurred or slurred transients and a general lack of clarity and purity of the sound or visual image.”
Misconception #5: There is some sort of conspiracy among audio designers that keeps them from producing a "proper" power supply that is not affect by power cable quality.
Answer: “This concept is like saying that if a speaker where properly designed, you wouldn't need to use a good quality speaker cable. PowerSnakes have been tested with the most modest of mid-fi equipment and the most exotic state of the art components. We have yet to find a component that cannot be improved by replacing the power cord.
As long as power supply design is based upon FWBRs or switching supplies, the power cord will always be significant.”
Misconception #6: High-end power cords just increase the circuit capacitance acting as a high-frequency shunt
Answer: “There are some power cords that ARE designed this way. Some even insert capacitors within the cable to further increase capacitance. This approach has some positives and many negatives including the reactive interference with the way many power supplies are designed.
Capacitance alone cannot account for the differences in a power cord's performance. There are some high-end power cords that are very effective that have virtually immeasurable levels of capacitance. These cables are usually designed around hollow tubes with the conductors inside. The conductors are several inches apart and cannot significantly affect the capacitance of the power circuit.”
Misconception #7: Power cords are just like speaker cables; always the shorter the cable the better.
Answer: “Some speaker cable designers would argue that a speaker cable below a certain length is not better. We will let them address the issue if they desire.
A speaker cable conducts an audio signal from the power amplifier to the speaker. The distance is quite small, on the order of a couple of feet to several feet. The quality of a speaker cable is determined by how well it can transmit the signal from the amplifier to the speaker without alteration.
A power cable on the other hand is not transmitting a signal. It is conducting A.C. power and its sonic superiority will be determined by its ability to deliver current (steady-state and instantaneous) and its ability to deal with the EMI effects of the components to which it is attached.
Since a power cord is composed of a hot and neutral wire that the component sits between, a change in the length of the cord will increase the size of the "buffer" around the component. In general, I would not recommend a power cord that is shorter than 3 feet or 1 meter in length. But subtle degrees of audio performance are not the only consideration when putting together an audio system. Esthetics is also important especially when the system is located in a beautiful home. I just point out the performance differences so that people can make an informed decision when determining the optimum length for their cables.
There is much more that can be discussed about power delivery but for the sake of brevity I'll cut it short at this point. On a personal note I would like to say that I was an audiophile long before I was a manufacturer of audio products. Before Shunyata Research I designed high speed networking devices and can tell you that there is a lot more money to be made in the computer industry. Like many of the manufacturers of high-end audio components, I design my products for myself and for the love of music. If other people like what I have created - great. If after trying our product you prefer another - great. There is a wide diversity of preference and subjective perception among individuals. Thank goodness there is also a wide diversity of manufacturers that create products to serve a variety of tastes.”
Caelin Gabriel
Shunyata Research Inc. End of quote.
I am now trying a few Transparent Audio power cords of type PowerLink MM2 (just bellow the OPUS) in my system. The effect on bass energy and slam is immediately noticeable.
