Is there a minimum length for power cords?


A cable manufacturer's website states the following:

"However, any length shorter than 1.8 meters (5.9 feet)will begin to degrade the effectiveness of the shielding and filtering capabilities; regardless of who is the manufacturer. Power cords are not like speaker cable and interconnects where shorter is better."

Does anyone have any thoughts or experience as to the validity of this statement?
owenlee
5FT is best.
With about 100 ft. Of wire in a transformer and another 100 ft. In the wall, the question should be how robust your power supply is for the amplifier and how much headroom you have is. The whole picture needs to be seen.
I personally like really long power cords. Most of mine are FOUR METERS long.
I have my stuff arranged to take advantage of long power cords. So the cords are not just piled up behind the rack.
My Furman REF20i conditioner os off tothe side and sso the four meter cords just reachthe top of thhe rack near me. Then the other way the cords just reach the amp between the speakers..

I make no claim that longer cords are better or not.
But for myself, the shortest cord I own is two meters.
Hi Elizabeth, what is your reason for liking long 4.0mtr power chords...
I like short ones. The 3 in my 2-channel system are between 20-24" each. You don't have to worry about them getting in the way ..... and they're cheaper :^ )
"However, any length shorter than 1.8 meters (5.9 feet)will begin to degrade the effectiveness of the shielding and filtering capabilities"

Sounds plausible to the layman I guess. If it's true it would then depend on how badly your set-up needed the shielding and filtering to begin with. This has been discussed in a similar thread here recently
http://forum.audiogon.com/cgi-bin/fr.pl?fcabl&1396218203&&&/Power-cord-length-
Hi Ebm, why is 5ft (2.5m) best :)
I would be curious to hear what other power cord manufacturers have to say about this? Could be true for one company but necessarily all of them.
Another manufacturer says no less than 3 feet. And some cable companies say that less than 8 feet is not ideal for speaker cables.
My short answer to the length question is ... 1.5 meters and 2.5 meters helps reduce SWVR

SWVR is ... Standing Wave Voltage Ratio or standing waves created by the difference of the minimum and maximum voltage the cable is conducting

I see two issues with poor SWVR ... first as with Power Correction Factor the further away you are from the Ideal number the less efficient the power deliver will be wasting energy ... this has to do with the deliver of the current

The second is Standing waves are created within the cable at certain intervals when all the direct energy from the source is not completely consumed by the Load and some is reflected back to the source ... here the reflected wave from the load back to the source collides with the direct waves from the source at particular intervals along the cable and a Ringing is created from this collision ... this ringing is created by the collision rate at which the primary and reflected waves fronts collide ...

How many times per second these wave fronts collide at a specific point along the cable creates what I believe is called a Beat Frequency ... the collision rate and creations of Beat Frequencies at these specific intervals are generally in RF region

It is not the standing wave that is creating the RF but the rate of collisions of the standing waves at a specific point along the cable that creates the Beat Frequency in the RF region ... reduce the collisions and you reduce the RF they create

The collisions points I believed are called harmonics and the first point is at the cables mid point .. the second harmonic of these collision is at the quarter (25%) points of the cable and so on up into the 3rd 4th and 5th harmonics until the energy is diminished

By using cables that are 1.5 meters and 2.5 meters long there appears to be a shift or optimizing in the points that these collisions occur at and a reductions of the Beat Frequencies ... reducing the RF that is created by the collisions

This is my back of the Napkin Theory and as you know ...

In Theory ... Theory and Practice are the same ... unfortunately in Practice they aren’t
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I think the manufacturers just want to sell us more wire.
Who's cables are we talking about here? I don't think anyone mentioned any brands up to this point. I'm guessing that the OP is referring to Shunyata, but it would be helpful to know for sure because I'd like to see if other manufactures give the same reason for the cables sounding better at a minimum length.
The Shunyata website says to not use a power cord under three feet long. Mapleshade says 8 feet is ideal for speaker cables - not more, not less.
... any length shorter than 1.8 meters (5.9 feet)will begin to degrade the effectiveness of the shielding and filtering capabilities; regardless of who is the manufacturer.
But on the other hand the resistance and inductance of the cord will increase in proportion to its length. Both of those increases can have adverse sonic consequences if large enough.

Personally, however, assuming adequate gauge for the application and assuming cord designs that are identical aside from length I suspect that in most and perhaps just about all systems none of these factors are likely to be great enough to make an audible difference for lengths of up to 8 or 10 feet or so, and perhaps more.

And to prove otherwise would require, as I see it, performing comparisons between different lengths of identical cords that are repeated multiple times, going back and forth between the two lengths to assure that the results are consistent and that perceived differences are not the result of extraneous variables or misperception. I doubt that very many audiophiles have done that, and even if some have I see no reason to expect their results to be applicable to different components, system configurations, and AC characteristics.

Regards,
-- Al
The unnamed manufacturer is LAT International. Found it with a quick search on part of the quote.
Here in New Zealand the power outlets within a house are configured in a loop. If a power cable is attached to the loop and it is shorter than 2 metres then it will be seen by the power supply as part of the loop. If the power cable is 2 metres or more, then it will be seen as a spur rather than part of a loop, and the electrical behaviour will be different.
If you have a dedicated mains supply - and you are running a spur from the main power distribution board, then you have created a spur and the length of power cable may be less important in this regard.
Yes, the manufacturer I referred to is LAT International.
my posts do not seemed to be getting posted???
I have experimented with ultra high end cables of lengths between 10" and 10' and have found virtually identical performance. I think you have to ask yourself that if length is so important, why are circuit boards built the way they are and how can a product perform so well with very limited distance between internal components (including the ones handling high current). Think about high end integrated amps versus separate components. Does having the extra power cords necessarily guarantee superior performance?
Dover, with respect to your comment I don't think a 2 meter or any other precise point of demarcation between what will be seen by the power supply as a stub vs. as part of the loop can be defined. It depends on the specific frequency component of the AC waveform that is being considered. And the distinction will only be relevant, if at all, at the very high frequencies of RF components that may be present in the waveform. With the resulting sonic effects, if any, almost certain to be unpredictable and inconsistent from system to system. I say that regardless of what you may have seen stated in certain marketing literature.

Davehrab, if you find yourself wanting a little extra income at some point, consider writing ad copy for cable manufacturers :-)

A minor point, btw: It's generally referred to as VSWR (often pronounced as "vizwar"), not SWVR.

Regards,
-- Al
Well, nothing's worse that finding yourself stuck with a pricey cable you cannot use because it is too short to reach the wall socket. I have 3 0f them because I USED to only need 5 feet.
07-07-14: Almarg
Dover, with respect to your comment I don't think a 2 meter or any other precise point of demarcation between what will be seen by the power supply as a stub vs. as part of the loop can be defined. It depends on the specific frequency component of the AC waveform that is being considered. And the distinction will only be relevant, if at all, at the very high frequencies of RF components that may be present in the waveform. With the resulting sonic effects, if any, almost certain to be unpredictable and inconsistent from system to system. I say that regardless of what you may have seen stated in certain marketing literature.
Almarg, my reference was from an engineer, I don't quote marketing hype. I agree the 2metres is arbitrary and I did not claim whether you should hear a difference. I simply stated that the electrical behaviour within the model for a spur is different to a loop.
From my own experience paying attention to power cabling and earth paths can yield significant improvements, particularly in lowering the noise floor and eliminating noise from other components on the "loop" such as video players, TV's etc. As a rule I have found significant improvements from running 1 dedicated line for the whole system, same length power cables for each component to keep the earthing arrangement as close to a star earth as possible to minimise potential differences. I have also found improvements sequencing the order of components as they go into the mains - from source to power amplifier - so the power amps are first off the rank, then pre then source etc. This methodology was proposed by Naim Audio, and I have experimented with it in many installs and found consistent benefits in non Naim systems.
With respected manufacturer MIT there are plain and networked cables of 2 meters. My licensed electrician friend said that to say the shielding is not effective for a short length of power cable is ludicrous.
@Yping: FYI, 2.5 meters is eight feet.
I have a 3ft Tara labs cobalt power cord, To my amusment, I sent Tara a E-mail asking about length of this model, Their answer?, The 3ft cobalt will have more resolution period than a 6ft cobalt power cord., that was their answer, However, I can tell you with 515 hours of burn-in that I have now, This power cord is not at all forward sounding, it's presatation is ideal, nor is it recessed, evadently, power cords seem to be different than say, a real short speaker cable where the sound does become forward, as far as speaker cables, I like 6ft speaker cable sound., cheers.
I bought longer than needed MIT Oracle PC's. I have been "so" grateful for the flexibility provided.The bit of extra length-on occasion-has "never" been even the least consequential--but it has been very revealing/informative/satisfying to be able to experiment due to having a bit of slack. Isn't that a common request.. to cut one some slack.
Why would length make a difference whether it's a power chord or speaker cable?
Why are my posts still being moderated?
IMO, no sonic difference with unshielded cords (1m - 5m).
"07-09-14: Yping
Why would length make a difference whether it's a power chord or speaker cable?"

With speaker cables and IC's, popular opinion is to keep the runs as short as possible to get the best sound quality. With power cords, some feel that the cable needs to be a minimum length to get the best sound. Personally, I find the idea plausible, but I don't feel I have the experience or the technical knowledge to make a recommendation, one way or the other.
Different lengths of power cord will produce different filter characteristics(combinations of capacitance, inductance and resistance which ALL cables have.)And this also depends on the type and configuration of the cable.
The best length for a given cable depends on a "CORRECT"
filter made of the cable parameters ( Example: Nordost recommends specifically 1.8 meters for one of their power cables to be best).If you don't have the knowledge and test equipment to measure(as most don't) Your only option is to try out,listen and use what sounds best to you. Jim C.
PS: Don't use AWG 18"Single Thin Wire" ones, even if they are pure silver! Use AWG 12 per leg at least, current and voltage transfer are what a power cord needs to do!!
High-end power cord manufacturers are in a bit of a pickle: if the power cords do everything that's claimed--that is, if they somehow make up for the "problems" in all of the wiring coming from your local power transformer to your wall socket--then why wouldn't a run of 2 feet, or 1 foot, or six inches (requiring only an el-cheapo extension cord) perform the same miracle, thus cutting down on the price of the super-expensive power cord material?

The answer is in the last phrase of the question.
Stewie, I'm afraid we've already thought of that. Duh!
Geoffk,"that" is mos def an indef ref.