In any "scientific" comparison test, you want to keep the test conditions as stable and repeatable as possible. Before the electrical engineers jump in with their recommendations, here's some of things you'd need to consider to increase the "validity" of your testing.
1. Stable Power -- dedicated outlet, same time at night: (i.e no variations in current from utility). Maybe even a PS 600 regenreating the same AC wave?? (Not sure if that's such a good idea).
2. Multiple double blind testing: You need to do the same thing many times and wipe out any personal biases by having someone else switch the cords and not tell you which one is on. Then you need to repeat the whole process with another listener ... and another.... well, you get the idea.
3. I can't explain the cooling off period (perhaps the electrical gurus on this site can) but it could be that a power cord "sets up" the component by alternating in some minute way the electrical components -- or in the case of an inferior cord, disturbing the balance, causing interference, or filtering out some needed component of the AC sine wave (sounds crazy -- but how else would you explain the "cooling off" period -- besides, we're dealing with electons here!) If this is true, until you can record and playback in SACD mode, you probably cannnot do back-to back reference testing. One suggestion would be to try to see how short the cooling off period can be made -- perhaps it's only an hour. Then, you'd have to take substantial notes, have others witness/agree with the results to again avoid personal/percieved or even unintentional bias.
So... now you know why it takes 15 - 20 years to get a drug through scientific testing and approval. Isn't science fun!
Just be thankful you're not required to do animal testing and then publish in a scientific journal.
For us audiogoners who would just like a little bit of logic and justification intermixed with "I CAN here the differnce" observations before we plunk down another grand on a PC, your observations, in as closely controlled conditions as are practical, are still very helpful and appreciated. And you'll probably do a better job then StereoFool, The Absolute Nonsense and those other "scientific" magazines we pay too much homage to. Please proceed!
