Power cords supplied with new equipment are required to carry a UL label. The gauge and number of conductors is stamped into the outer cable jacket every foot.
Most original equipment manufacturer supplied power cables are three conductor. A hot, a neutral and a ground, usually twisted together to help reduce RFI and 60 cycle (hum) pick up. If the manufacturer wants to spend a little more, their stock cable might include a foil shield around the three conductors. Unfortunately it's really pointless for them to do anything more.
And it's not about the money – here's why:
Underwriters Laboratory requires power cords have a ground conductor that is connected to ground at EACH END of the cord (via the ground pin on the wall plug.)
This provision allows UL to indemnify (underwrite) the manufacturer against liability claims by the end user, for electric shock from a faulty power cord.
So what's not to like? Well, a long piece of wire that's grounded at each end becomes (guess what!) an ANTENNA! Depending on its length and orientation, the wire will pick up all kinds of electromagnetic radiation (noise) and, it will induce that noise in any other (ungrounded) conductors that it's in close physical contact with; which will in turn send that noise straight into the power supply of your high-end audio equipment! And this is why you won't find expensive high end aftermarket power cords sporting a UL label!
So I think the manufacturers deserve a little bit of slack when it comes to OEM power cords! However, before you totally give up on the power cord that arrived with your new audio gear, there is something you could try, and in the words of the late John Prine "It don't cost very much, and it lasts a long while!" (and you can try it without modifying the stock cord) as follows:
You need to "lift" (disconnect) the ground at the EQUIPMENT end of the stock cord.
First the quick method: cut off the IEC plug at the equipment end of the cord and install a new IEC plug with only the hot (black) and neutral (white) conductors connected to the corresponding hot and neutral terminals of the new IEC plug. The ground conductor (green) should be cut a little short of the new IEC plug and not connected. You have just turned a stock power cord into a respectable audiophile power cord; if do this with all your stock power cords you'll wind up with a much quieter system!
If you want to try this without modifying the stock power cord, just make a little pigtail using a male and a female IEC plug wiring only their hot and neutral terminals. Then spend an evening A-B ing all of your stock power cords — cheap thrills!
