Are manufacturer AC cables good enough?

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! 

As part of moving equipment from one rack to another I at last connected a Pangea AC 14 to the Ayre VX-5 Twenty amp -- I've misplaced the PS Audio AC 3s and the other AC 14 in the mess I've made during the change over.  I have a bunch of similar looking black cables I grab as needed so I'm not sure what cable came with what piece of equipment.  I think I do hear a bit more detail with the AC 14 installed.  I'll continue to search for the AC 3s and other AC 14.

db  

My "thinking" and experience have been at odds when it comes to AC cords. Thinking tells me that "wire is wire" and so long as it can carry enough current, it can't possible sound any better. My experience is the polar opposite. In every case, no exceptions, upgrading from the stock power cords has dramatically improved my enjoyment of music. Maybe my "system" was no better, but the music was most often far move involving, emotionally engaging and just more real. Switching AC cords worked on a Rotel CD player, ARC Ref 3 preamp and perhaps most dramatically, on a McCormack DNA 1 Platinum revision amp. I have seen vastly better picture quality on a plasma TV, heard more detail from an ARC LS9 preamp and on and on. There is science (better understood then in the past) as to why good AC power cables do what they do. The merits of all sorts theories can be debated. I have decided just to ignore the science, for the most part, and the debates, and simply enjoy the music. 
   

It's 2020 and people are still arguing if cables make the difference.  Unbelievable.

Regarding Ayre and Cardas, it makes perfect sense to me.  I used to have Ayre CDP many years ago. It had a clean, sterile sound. In the end I used it with Cardas Cross and then GC, which made it a bit better, warmer and more, well, human. But I never came to liking the Ayre sound. 

I am not trying to imply that all Ayre sound like that, I have no idea how their current line of products sound, probably they have some fantastic amps, but that old CDP somehow deters me from looking back at their products. Probably the worst CDP/DAC I have ever had, apart from, obviously, some cheapo stuff.  

I sold Ayre and bough a used Burmester, which btw came with their Burmester power cable. The CDP is gone, but I still have the cable. The sonic picture of that cord I would describe as "hard-hitting" with a pronounced presence range, and this effect was pretty consistent with every CDP I tried. It is so different from Cardas, it's not even funny.

I should try with my current DAC just for the sake of it, but since I am not too much into cables, it will probably keep gathering dust in a cupboard.