Power cords makes difference-Why?

I just discovered to my amazment that even power cords swap with the same high-end brand of equipment makes a difference. My story follows , I would like someone to shed more light on the phenomenon.( I know there exist power cords costing thousands, but never bought in to it.)Recently I added a surround sound preamp (Classe SSP-50) and multi channel amp(classe CAV-150)and center and surround speakers(Dunlavy SC-1 and SC-II'S). I have two channel system consisting of Classe CDP.5, Preamp CP-45,Amp CA-400 and Dunlavy SC V's as main speakers.The power cord on the SSP-50 has a little larger dia then the preamp CP-45. Last few weeks I thought I was using 'better' power cord with the CP-45. Everything else remained same for two channel(SSP-50 isolated) and the sound stage changed for worse.I was scraching my head frustrated thinking if any thing else I did could change my Audio nirvana. Then I recalled the powercord swap and quickly changed back to thier respective cords and wallah: My original sound was back.So my question: What constitutes a great power cord? Thanks for your advice in advance.
There's no simple answer to that. They all transfer current to varying degrees, and achieve noise filtration in different ways, and to different degrees. Also, the noise present in one's AC will vary from location to location, besides the manner in which the supply is fed into your house, and the wiring in your house is also a big factor. Then there are the outlets...
Thanks, Carl_eber. Let me ask it different way. Do the Hi end manufacturer design power cords specifically for the component? and that is why I experienced the difference in sound quality when swapped.!!
Not usually. You just have to try different ones, until you find a match, that lets the system perform optimally in all parameters. It's not easy, and takes much time.
If you can afford it dedicated power circuits for your rig with a seperate ground makes a huge difference. If your utility supplies noisy power a big honking isolation transformer is good too. The other alternative for noisy power is PS Audio Power Plants. I use all of the forementioned and it made a bigger difference than exotic powercords and given their cost not a significant difference in overall cost. However there are many different forms of electrical gremlins, utility service problems and wiring shortcomings. (Where I live I have them all.) Finding the best approach for your power conditioning needs is, as Carl says, not easy. There have been several discussions on audiogon of dedicated power approaches with an albertporter post, as usual, among the best.
There is a lot of information on this subject at the Vansevers website.
Good replies to your question. Sometimes in trying to understand the solution to a problem, like a better power cord can be...it is good to either understand or be aware of the problem. Of the many things that can be a concern with the AC power going into your components...the one that is easy to grasp is the idea of wire and RF. If a person wants to receive a distant FM station, it is best to put up a good antenna..., well, the huge amount of wire running through a home is much like a massive antenna for FM, AM, Ham, CB, ticks and pops from household electronics...let alone what is feed back onto the line from very powerfull motors on the furnace...and the list goes on. A line comming in...kept short for the stereo..is a great suggestion, one of the power plants, or the like is another good idea..and the power cord IS the last line of defense. I have had good luck with the high-end Nordost, but almost any upgrade is better than none. Best of success.
Thanks to all of you for your inputs. The power plant I have heard ( and read)a lot about lately.I am referring to the PS300 and recent bigger models. What I can't decide is waht model to buy (try first). Does it have a greater effect on the front ends only or Does is also have to be for the amp? ( As my power requirements are very high for the amp, 800 w in 4 ohms for the Dunlavy V'S.) Should I buy the PS300 for the front ends first or buy their biggest model PS2000? for all? I have read mixed reviews on PS600, It seems PS300 somehow comes ahead.
The first thing to do if you can afford it is run dedicated lines and put in quality hospital grade wall outlets.Once you have done this then you should move on to other power tweaks.This is generally the best bang for your buck.And usually has the biggest effect.
I also have SC-V's which I dirve with high powered tube monoblocks. The three things that did the most were dedicated lines in balanced congiguration for the power amps. A edicated star ground. Dedicated lines in a balanced configuration to two PS-300's one for my digital input chan and one for my analog chain. I doubt that unless you have really awefull power or that you have both very high RFI and very susceptable amps that the high powered PS Audio Power Plants would improve your poweramps mor than dedicated lines and a good powercord.