Are manufacturer AC cables good enough?

I recently substituted the stock power cord I got with my Mytek BB with a Shunyata Diamondback I fished out of the closet.  I won't tell you how it got there because I'm not really sure.  Short story shorter...  Dad gum, it actually made my stereo sound better.  Practically every single audiophile parameter, from soundstaging to understand-ability of lyrics to orchestral string tone, got a five to ten percent boost.  This happened with every source, as I use the Mytek as my phono amp in addition to using its streamer/DAC functions.  Huh?  Wha?

@fastfreight

I wonder how many of the nay sayers who claim power cables do not make a difference have even tried upgraded PC’s? To me, they either have not tried or can not hear. And it is usually them who cite science to explain away any possible benefit.

Yes, I have tried upgraded PCs. For instance a selection of Shunyata power cables of varying price. I tried them against the stock power cables in my system.

And with the really expensive cable I heard a difference! An obvious difference! Smoother, richer, darker, bigger soundstage, all that good stuff!

But then I did something more. I actually decided to trust my hearing.

I mean...*really* trust my hearing. Not the "trust my ears* with fingers crossed behind my back, the one where I also used my eyes and knew which cable I was listening to.

I had a friend help me do a blind test shoot out in which he could switch between the cheap, stock cable and the shunyata. Well, once I was no longer allowed to peek, those "obvious" sonic differences suddenly didn’t seem to be there. No matter how I tried I couldn’t hear any difference between the stock and the expensive cable. My guesses were random.

It was another fascinating lesson in the power of sighted bias. One that many audiophiles never bother to learn ;-)

I certainly did not want to hear the difference I did, it would have saved me money. I did try and I did hear...and not subtly.

Yeah, I remember thinking that too. ;-)

No matter how I tried I couldn’t hear any difference between the stock and the expensive cable.

You don’t have to try and convince me. I could tell from the beginning you weren’t any good at this.
;-) 

I watched a video of Floyd Toole giving a talk on speaker testing when he was discussing how they do testing he mentioned if someone tells him their experiences he asks how the test was administered if it was sighted he said in my mind I simply dismiss it and nod because I know it’s a useless test. Sighted testing is completely worthless in understanding the effects and differences in products not just audio.

Controlled blind testing works for coronavirus drug tests as currently ongoing when there are very large randomized samples. For audio not so much. There is no comparison between medical controlled blind tests and audio controlled blind tests. Primarily you can’t control audio tests easily. You might think you can but you can’t. And if there is only one blind test the results are meaningless, I.e., no conclusions can be drawn. Come on, guys.