hospital grade or commercial grade receptacles ?

If power receptacles make a difference (and I doubt it) you would be better off using ones designed for high current high voltage applications, like you stove or clothes dryer. These have contacts with much greater contact area, and some have a twist-to-lock feature that provides a wiping action for the contacts.

Another pointless battle between those who hear differences and those who don't- which has to depend, I have come to believe, not on differences of hearing but on the resolution and nature of the equipment used. In my case, Wattgates and FIM outlets sound different from one another in easily described ways, and better than stock, by far. No competition, no subtle differences, night and day stuff. In my experience, too, although not with outlets, I don't like the sound of cryo'd components: they tend, consistently, to sound more forward, with less air around images, than stock versions of the same. It's a matter of taste.

To those that say outlets (or power cords, or plugs) have a sonic signature... how do you believe this happens? You have many, many feet of 12-14ga Romex (or equivalent) in your house. Some of you have aluminum wires. Then you assume that the termination of all of that simple, cheap wiring at the outlet, as compared to a different termination (that can be shown to have inconsequential resistance), has a sonic signature? This is akin to astrology. I have no doubt that some people believe they hear differences, but the far and away most likely scenario is that there are no differences between outlets (that function properly within their specs), no sonic differences attributable to cryogenics, and that same reasoning can be extended to power cords with reasonable gauges for the loads involved. The difference you think you hear isn't real. It's in your head and nowhere else.

Even if you assume, just for the point of argument, that there is a difference in sonics that could happen between outlets, how would that difference survive the voltage step-down of the component's power transformer? Or the rectification to DC? Or the capacitors? Before all of those electrons hit any sort of active circuitry?

Doesn't this seem unreasonable? Did all of you sleep during high school physics? I'm assuming there's no one arguing here that even vaguely understands electrical engineering...

In response to Irv,

I'm not saying that physics doesn't matter. And I'm not a scientist-- although I am a professor, and therefore used to thinking skeptically, and demanding proof from myself and from my students in our work in the humanities. And heck if I know why some outlets (and power conditioners, and power cords) sound different. But the fact is, they do (at least through my Audio Research electronics, Vandersteens, and good cabling: your equipment might reveal more or fewer of these differences. Some equipment, including very, very good equipment, doesn't change much when altering peripherals). And not a little, and not subtley. You don't have to be a true believer, or a crank. This is audible, and easily audible, to people who don't care one way or the other (such as my wife). In my case, FIM outlets were too dark sounding for the associated equipment-- a phenomenon many others attest to independantly-- and Wattgates were much clearer and brighter (the same applies). As with so many other things in science, one notices the phenomenon first, and then hopes to find the the underlying mechanism that explains it. Although we try to pretend it isn't, much medical research is based upon this fact.