Here's a little story of mine. I had used Virtual Dynamics Power 3 for several years. I am open minded, and willing to accept what I hear. And I do hear differences various interconnects and speaker cables. But I haven't really heard difference in power cords yet. The only reason I was using VD cord was because I got a good deal, and thought it wouldn't hurt the sound. The main drawback using VD cable was the weight and stiffness of the cable prevents good contact on the wall. When I moved into my current home early this year, I did not use VD cable because the location of the component made it impossible to use such a stiff cable. I didn't think I was missing anything without VD cable then.
A few weeks ago I rearranged the components, and decided to put back VD power cord. My friends and I listened to music for a while, and thought the sound got better. It has gotten decidedly more open, transparent, and clear with VD power cord. We then switched the cords back and forth to confirm that the power cord really caused the change in sound. And then we thought it would be fun to switch the power cords in DBT environment. So we did. We took out a blindfold, and did several iteration of the same music that we thought clearly showed the different power cords while the listener was blind folded. Unfortunately, we all failed to identify the cord in DBT environment.
We were all in shock afterwards. Then we did more iteration of power cord switching without blind folds, and I was not really sure that the sound really changed with VD cord any more. I then sold my VD cord next week to raise funds for something else..
We can draw our own conclusions on this story. Wearing my "skeptic hat", one thing I have realized was that placebo effect, and the power of the brain can really influence our perception. Playing the same music on the same day using the same equipment can yield drastically different impressions. First we all thought the sound was different and better with different power cords. After the DBT "incident" I wasn't sure if I heard the difference again.
Another thing that I would like to add, now wearing my "open minded" hat, DBT is very hard to conduct, and the result really does not prove one thing or the other. There is a nice story of JA from stereophile about conducting DBT on two amps, which pretty much concludes that the results of DBT is inconclusive. I would agree with him. With blind folded, and under the pressure to "guess" the correct answer, I got somewhat nervous and really could not concentrate in listening. Also we did it as a fun, not as a serious experiment.
I remain open minded, and do not want to dismiss the power cord theory. In fact I happened to have just acquired three VH audio power cords a couple of weeks ago, two flavor 4 and one flavor 1 for my Shunyata Hydra, EAD PM2000, and CAL front end. The hope was to "open up" frequency extremes and remove veiling on my newly acquired EAD amp. Flavor 4 for CAL was a bonus, just in case the new set of power cords really does wonders to the sound. It's been burning in for a couple of weeks now. So far I can't say that the new set of power cords improved the sound drastically. But it's still too early to draw any conclusion. Stay tuned.