Is it all in my head??

An ee told me once (and I’m not nearly an ee) that sound was primarily determined by power-vs-length-vs-geometry. Other things like noise cancellation or group delay caused by insulation thickness and material also enter into it. The actual calculations for that sort of thing are often proprietary and not given up easily by those in the know. But, this tends to mean that different components that have different power draws tend to require different power-vs-length-vs-geometry solutions But, the rest of us have to struggle along when it comes to DIY...or copy what we see that works for a given app, or whatever.

I've built speaker cables and IC's, but have never attempted power cords.

my speaker cables vary wildly with geometry... i use the same 12-awg cable for all of them.. i've built about 4 pair so far for critical listening.  

One thing I believe I do know by now, is that the insulation known as PVC is just plain terrible...I mean it’s hot stinking garbage...just no good way to apply it for sound quality’s sake. It’s that smooth, usually black or dark grey, rubbery material that you often see on lower-priced IC’s, sometimes on speaker cables or even pc’s. Almost all the IC’s that come inside the box with new gear have it. It’s smooth in texture, has a matte finish, and gives a little bit to the touch like neoprene, except PVC has much finer air cells within it.

PVC destroys air, openness and the sense of atmospheric space, not just through the mids and highs, but down into the lower mids and can even obscure some bass detail. It has that characteristic "dead", "lifeless" or "rubbery" sound to it that you usually associate with cheaper wires. The good news is that whenever you simply strip off this material down to whatever material is underneath, you breathe massive amounts of life back into the sound and the music. With XLR cables the underlying material will likely braid shielding, in which case you need to cut carefully without nicking up the braid too much. But, it’s amazing how much even cheapie wires will benefit from this! Which makes it easy to try out if you have a pair. But, I’ve tried it enough times now to know that whenever I buy any wires with this jacketing on it, I know definitely that it’s coming off as soon as I buy them.