Power Cord Length

Here's one for the electric wizards to kick around. Whilst attending Axpona this weekend I was doing some power cord shopping. At one particular display I was being told by a very well known cable company representative, I'll not mention the name so it doesn't influence any responses, that the rule of thumb is that in order for the pwr cord to be effective it needs to be at least five feet long. This allows the current to be in the cord long enough for it to be effective. Ok, I'm really dumb when it comes to this sort of thing so maybe I said that in the most simpliest of words but that's pretty much how it was explained. Anyone care to elaborate on this good or bad?

Showing 1 response by humand

I love how people who have never tried "fancy" AC Cords are so sure they cannot make an audible difference. I hate that they do indeed make quite a difference in most cases but they are terribly synergistic and it is difficult to recommend any one overall. Just the stiffness of the local electrical grid can be quite a factor as well as the associated equipment (and appliances) on the same lines. Damned if the ac outlets themselves seem to affect sound too.
 One poster is right on the money. They are indeed a parasitic element to the power supply. They can be designed as filters (or include filter networks), used for current or voltage storage and at least one claims negative impedance while others claim shielding makes the difference. Then there are those who claim they act as a transmission line so the geometry and dielectric matter there. Different metals, conductor shapes, and terminations also seem to have their own effect. Resonances (all finite length conductors have) based on length and propagation speed can be seen with an oscilloscope and frequency sweeps or a network analyzer. There are mechanical vibration and microphonics to deal with; even static charges are dealt with in some cases. Wire loss or DC resistance is a fact in any case and varies with frequency.
 Regardless of explanation or principals whether or not it is audible to you should be the criteria. We just do not know it all and our system of measurements are quite limited and lacking IMHO. Find a friend and try some blind testing if you can. Mixing and matching is part of the art.
 It must also be said that many designers are not going to give away their particular paradigm or trade secret while others do have white papers and measurements galore it is a complex issue. Ultimately it is your own listening judgement and I urge you to try experimenting. The  relatively inexpensive DH Labs bulk DIY cable is a great place to start.