Longer Power Cords Sound better?

Tplavas: Without going into a detailed characterization of the sound of the Mainsstream (although actually, your adjectives, though not the entire story, do happen to apply very well in this case) -- and I hope without being too cute in answering the question -- the simplest and probably best way I can describe the difference I found attributable to length is that the longer version sounds the same as the shorter version only more so, if you take my meaning. With this particular cord, in these lengths and in my system, to me that's a good thing, but I can also imagine by extrapolation the possibility of going overboard (something that could be said about any filtering). However, without a 30ft. cord on hand to compare that's only a guess on my part, and perhaps as has been suggested things just keep getting better and better, or maybe we simply reach a point of diminishing returns without going over into detrimental effects. (Unlike Leonx, I didn't find any loss of real resolution with the longer cord, although the reduced brightness, which I assume could represent reduced modulated noise, might be mistaken for such.)

PS -- I regret to have to add that for anyone interested in trying this cord, be aware it's a model which has been widely counterfeited on the secondhand market, as I found out the hard way before getting enlightened.

Zaikesman,

The adjectives I used, though fairly broad and basic, were chosen because that's my experience with the vast majority of PC's. So if, as you stated, there was a reduced brightness in the longer Van Den Hul cord, how would one explain that same tendency in cords that feature no 'filtering' of any kind?
The answer is in the inductance and capacitance factors that result from increased length. It's no more complicated than that. Longer cords get 'warmer' with every foot you add, although how rapidly you hear the change depends on the specific geometry of the cord. The VDH cable is an outstanding design, with very low inductance, so it's losses in resolution and dynamics should be more gradual as the length increases. Other cords, which have higher levels of Inductance per foot, will yield a more rapid change as the length increases.
A properly designed PC should be resistant to noise, but if the changes in sonics we're hearing are strictly from filtering out that noise, then where are the measurements to back up that idea? I've seen plenty of powerline conditioners that give specs on their noise filtering capabilities, but have yet to see numbers on a PC. I don't think that's coincidence.
IMO, RLC factors rule the roost when it comes to PC sonics. They don't explain everything (like why cryoing 'sounds' like lowered inductance, but isn't measureable), but they seem to get us most of the way there.
Again, JMO.

Tplavas wrote:

"...if, as you stated, there was a reduced brightness in the longer Van Den Hul cord, how would one explain that same tendency in cords that feature no 'filtering' of any kind? The answer is in the inductance and capacitance factors that result from increased length.

"...A properly designed PC should be resistant to noise, but if the changes in sonics we're hearing are strictly from filtering out that noise, then where are the measurements to back up that idea?

"...IMO, RLC factors rule the roost when it comes to PC sonics."

The RLC factors themselves constitute a filter. All cables have RLC factors of course (including all the miles of it leading to the house), so all cords must act as filters in some way, but not all cords intentionally strive to arrange the factors so that the cord constitutes an effective filter for significantly reducing noise from the AC powerline. But that filtration effect, if so designed, is what reduces the noise (other than induced noise which is reduced by the shielding). That these RLC factors, and hence the degree of filtering, and hence the degree of noise reduction, will all be greater the longer the cord, is exactly what vdH posits for their particular cord, and is why they won't sell a 1m version. I own another variety of cord, not purported to act as a powerline filter, that do not affect the sound in the way your adjectives suggest, but instead tends to make it brighter sounding, among other qualities. However, whether this cord becomes mellower in longer lengths is something I do not know -- maybe just the opposite happens. Bottom line -- although I find your contentions somewhat obvious while also a bit self-contradictory in some details -- I don't think we fundamentally disagree here: Whatever a given cord does, a longer one will probably do more of it, and this could be either a good or a bad thing.