Power Line Disturbances
Optimum performance of the highly sophisticated electronics
that comprise todays 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sometimes outdated, system of power generation plants and
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
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
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
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
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
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
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.