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?
128x128owenlee

Showing 2 responses by dover

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.
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.