Newsgroups: rec.audio.tech
Subject: Re: Power cords
References: <[email protected]>
From: Tomi Holger Engdahl 
Date: 28 Apr 2000 15:03:50 +0300
Message-ID: 
Organization: Helsinki University of Technology, Finland
Lines: 113
X-Newsreader: Gnus v5.6.45/Emacs 19.34
GG  writes:

> Found the following on a website of a company selling these very
> expensive power cords. Is there anyone who is really stupid enought to
> fall for this total idiotic nonsense?

According some HIFI magazines and news posting and fact that
there are many idiotic nonsense products like this been on that
markets for ages, there must be some stupid people whi fall into 
this. Propably quite many such people.

The power cord thing seems to be very stupid. Those people who
tweak power cords are very much overly pointing to one very short
piece (few meters) of the whole electrical power supply chain. 

If they attach that very highly overpriced esoteric 2 meter power
cable to their system, they end up having the following power system
from the nearest power company distribution transformer
(quite typical situation):

- 20-200 meters of cable from power company transformer to
  your main electrical panel, that wire is propably shared
  with more than one building/apartment
- 1 meter of wire and copper bard in mains panel
- few centimeters of very thin wire inside normal fuse,
  typically 2 fuses on the way from mains input to outlet
- 5-25 meters of wire from mains panel to power outlet
- 1-2 meters of that fantastic extra expensive special cable
- thin wire in the mains fuse
- test of meters of thin copper wire in mains transformer

It would be quite interresting in this scenatrio that 
changing a short pice of wire (1% of total length)
in this would make any radical changes in the system performance.
If that short pice of cable makes radical changes, then plugging
the equipment to different outlets would be something even
much more radical.

and commeting the quoted part:

> music signal. And because it is the first component affecting the
> signal�s amplification, the power cord is arguably the most important
> because unfortunately "distortion begets more distortion". 

Wrong argumentation. The standard power cords are good enought
for their job of carrying the power from mains power
outlet to the equipment well. 

> Signal distortions caused by upstream components such as the a/c power
> cord are amplified through the rest of the music chain.

Power cord itself does not cause distortion. The main main cause
of AC power distortionscaused by your HIFI system is the power
amplifier power supply (transformer+rectifier+filter capacitor).

> The power cord affects the amount and delivery speed of current
> available to your equipment�s power supply. 

In mains powered equipments the equipment power cord does not much
effect those propertied. Few meter logn cable properly approved for
this kind of application will do the job well. The potential
for current sypply on your mains outlet is determined by other
factors.

The only place where power cords have noticable effect on the
available curretn are car HIFI installations where thick power
cables are wired from cas battery to amplifier. Here the resistacne
of this wire is the major current limiting factor.

> A music signal typically
> can have a dynamic range requiring a 10-to-1 power ratio to accurately
> reproduce. These dynamic contrasts can occur instantaneously. Your
> equipment not only needs to have the capacity to supply enormous amounts
> of power during dynamic peaks, it must be able to recharge very quickly
> because, the music doesn�t wait.

The power supply of the amplifier is designed to cope with this.
The capability of mains powered amplifier to perform as described
is effected almost entirely of other facts than mains power cord.

The amplifiers do not take and should not take very high current
surges from the mains power. 

> Continued careful listening reveals other phenomena. First, one notices
> a loss in soundstage accuracy. Common symptoms include featured
> instrument and vocal images being spread across the entire front
> soundstage. Image depth and height dimensions also become compressed. A
> harsh stridency is apparent during dynamic peaks in the
> upper-midrange/lower-treble range.

Careful reading and believing of this snake oil thing reveals you to 
belive that you hear those thigns even though there are no such 
changes in your system sound.

> Phase shifts destroy the directional cues inherent in the
> original recording, and cause much of the harshness heard particularly
> during CD playback. This type of distortion is not correctable with
> typical controls available to us in home audio systems. Therefore, its
> sources must be eliminated from your system to reveal the music�s
> natural spatial and harmonic character.

This prt of text is true, but those effects described are NOT
caused by the power cables. Phabse shifs are cause by audio
filters, equalizers, speakers and typical controls on home audio
systems. If those problems exist sources must be eliminated from your 
system to reveal the whole music. But the source which needs to be
eliminated os not the power cord.
 

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/