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Home > Resources > How-To's > Power Line Disturbances Checkout | My Account | Help

How-To's

Power Line Disturbances

Optimum performance of the highly sophisticated electronics that comprise today’s high-end audio or video system is dependent upon a clean and stable supply of electrical current. Conversely, the modern day world, with its myriad of electrical devices, does much to degrade the electricity that we receive. The ever increasing demand for electrical power is asking more and more of an already overtaxed, and sometimes outdated, system of power generation plants and distribution grids.

Major metropolitan areas of the country (where most of us dwell) are headed for a growing number of power related problems (as populations swell) with significant increases in both frequency and severity of power line disturbances. An article in the Wall Street Journal predicts a significant lack of generating capacity for many areas of the country including the entire Eastern Seaboard, the Midwest and the Pacific Northwest, resulting in major power related problems. It stated demand will outstrip supply by 3 - 13 %, depending on geographical area (who knows what that number is today!). This prediction compared with a 1 - 12 % surplus in the late nineties.

So there, in a nutshell, we have the problem. The audiophile community has now come to grips with the effect of these electrical artifacts on our treasured passion. Let us begin a short journey into this little known world, in the hopes that we may arrive at a better understanding regarding the effects of power line disturbances upon our enjoyment of reproduced music in the home.

In much the same way that a high performance race car depends upon a continuous supply of high quality fuel for peak performance, your audio and/or video system relies upon the electrical "fuel" it receives from the wall outlet. If the supply runs short, or is of poor quality, performance is lost.

The electricity generated by your local power plant should, ideally, be a precise and steady 60 Hertz 120 Volt sine wave. No "glitches" or noise should be present, and the voltage should remain a constant 120 Volts despite load demands. Unfortunately, our ultra-sensitive equipment is rarely, if ever, operated under such ideal conditions. 

As the electricity travels down the transmission lines from the generation point, many undesirable effects are likely to occur. These include voltage fluctuation (sags and spikes) and the intrusion of various forms of noise (Radio Frequency Interference and Electro Magnetic Interference). During peak usage hours for, example, many other folks just like yourself create a high demand for electrical power. If you are one of the many listeners who report better sound quality when listening late at night, you have experienced how varying load demands affect audio quality. When the demand is excessive, the voltage drops. If the drop is significant, a condition known as brownout occurs. A brownout may last only a few seconds or may continue for hours. Undoubtedly, you have noticed the momentary dimming of the lights in your home as the refrigerator, furnace or air conditioner starts. This short-term, high demand for electrical power temporarily lowers the voltage throughout the house, creating a local brownout. This condition, if severe, robs your audio equipment of the voltage necessary for best operation.

In addition to voltage fluctuations, it is likely that numerous other "power line gremlins" are present in your electrical service. Various types of noise are common additions that find their way into the electricity during its treacherous journey to us from the generating plant. Once the electricity reaches the homes' main junction box, another hazardous trip begins for our little electron friends. Anything plugged into an electrical outlet has the potential to affect the amount of noise on the line and reduce the peak current available. Appliances such as refrigerators, air conditioners and the like are particularly likely to degrade the quality of the AC line by adding noise or momentarily producing a voltage spike or sag.

As far as I know, no one has ever undertaken a study of the effects of AC line noise on audio equipment, although studies have been done with computers as the focus. The results show that significant, even disruptive, problems are caused by these AC line related problems. Spikes, sags, surges and brownouts have caused contamination of data and cumulative hardware damage.

Back in 1974, an extensive evaluation of AC line problems was carried out by two scientists at IBM. The study was based upon data collected over several years in 49 different locations. Although the study focused on the effects of these disturbances on computers, the results still hold meaning for audiophiles. What follows is a brief synopsis of their findings.

Disturbances were broken down into four categories: 1) OSCILLATORY - Decaying transients caused by the switching of power factor correction capacitors and other utility network or load switching. A monthly average of 62.6 incidents accounted for 49% of the total number of disturbances. 2) VOLTAGE SPIKES - Caused by lightning, by power network switching and by user equipment operation. A monthly average of 50.7 incidents accounted for 39.5% of the total number of disturbances. 3) UNDER VOLTAGES and OVER VOLTAGES OF GREATER THAN 1 CYCLE - Caused by the application of heavy loads to the line, by faults and the resultant actions of fault-clearing devices. A monthly average of 14.4 incidents accounted for 1 % of the total number of disturbances. 4) OUTAGES OF GREATER THAN ONE CYCLE IN DURATION - Caused by faults within user networks or by a breakdown of utility power transmission equipment. Monthly average of 0. 6 incidents accounted for 0. 5 % of the total number of disturbances reported.

From this overview, an important fact emerges. A surprising 88.5 % of the problems noted are noise related (category 1 and 2), and most likely to degrade audio/video system performance. These disturbances are further defined as being in the typical frequency range of 400 to 5000Hz for oscillatory, decaying transients and l0kHz for voltage spikes. Both types of disturbances may occur as either transverse-mode (between hot and neutral conductors) or common-mode (between ground and either hot or neutral) noise.

Keep in mind, folks, this study was done in 1974. I'm sure you can imagine how dramatically worse conditions are today!

Exactly what does all this mean to the listener? While we don't know the whole story, we do know that power line disturbances do in fact adversely affect the quality of sound we can expect from our stereo system and picture quality we see in our display devices. Noise on the AC line can manifest itself in the form of "clicks" and "pops" or, more detrimentally, as subtle distortions that veil the music, adding the equivalent of "sonic grunge." Visual artifacts are many and varied. Low voltage may cause similar problems besides robbing your power amplifier of the "juice" it needs to perform up to spec. The power output of your amplifier is directly dependent upon line voltage. As the voltage drops below the point at which the manufacturer determined the power rating, the available output drops off, sometimes severely.

Possibly even more sensitive than power amplifiers to AC line problems are the signal front-end components - preamplifier, CD player, turntable and other signal sources or processors. These units have much smaller power supplies than do amplifiers and consequently have a lessened ability to filter out the line related problems that degrade their sound. The potential for signal degradation appears to be great in these relatively unprotected units.

The specific ways in which AC line problems conspire to wreak havoc on our systems is still not completely clear. It is an unquestioned fact, however, that negative consequences are an expected result of their existence. From simple sonic degradation to the possibility of premature hardware failure, the range of possible effects are quite undesirable. One can be certain that the problem of power line disturbances will get worse before it gets better, if it ever does. It is then up to us to fend for ourselves by utilizing some form of line conditioning technique to ameliorate the effects of AC line disturbances.

At this point many listeners feel they are unaffected by power related troubles simply because they don't "hear" them. AC line related issues almost never manifest themselves in obvious ways, such as hum or noise. No, they're far more insidious than that. AC related distortion hides in background, resulting in haze, grain or glare. Many times people associate these ills with a component, when they are much more often power line related. Installing a good line conditioner will almost always breathe new life into a system and uncover a wealth of hidden detail. Don't have a problem? You probably do, but it's only when you remove the problem will you hear what you've been missing. Reminds me of a verse in a Joni Mitchell song: "You don't know what you've got 'till it's gone." 

Glossary of Terms

Blackout - Sustained lack of AC line voltage.

Brownout - Sustained period of low AC line voltage.

Fluctuation - A surge, sag or brownout condition.

Line Noise (EMI/RFI) - Electro-magnetic Interference and Radio Frequency Interference. Can be caused by a variety of sources including: static electricity, household appliances, radio stations or other broadcast facilities, military or civilian radar, faulty electrical fixtures and power transformers.

Sag - A low voltage condition of short duration.

Spike - Instantaneous over voltage condition superimposed on the AC line. Large scale spikes from a thunderstorm, smaller spikes generally result from appliances.

Surge - Sustained period of over-voltage.

Line Conditioners - A general term referring to any device designed to decrease AC line related problems.

UPS - Uninterruptible Power Supply uses batteries to provide backup power in the event of a blackout, or provide stable voltage during a brownout or fluctuation if the unit also features voltage regulation.

Voltage Regulator - A device designed to stabilize line voltage. Many different types exist, some are more accurate than others.

 

 

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