Can a better power cable make a difference if NOT plugged directly into an outlet?

I use Pangea AC 9 SE and AC14 SE cords, at present.

This setup has been quiet and hum free. 

Improvement in power cords does not mean fixing audible noise issues you can hear, such as hum, buzz, distorted sound. Coincidence I received the following email newsletter this morning from Paul McGowan of PS Audio, copy/ paste below:

———-

Crossing wires

When my parents were coming of age, the telephone system used a massive number of patchbays and operators connecting one phone to another. On occasion, they would make the wrong patch which is where the term crossing wires comes from.

Not only telephone operators cross wires. 

In a recent video of mine I speak at length about how USB noise impacts audio quality. I further go on explaining that adding a USB hub or stepping up to our new galvanically isolated MKII DAC is needed to clean up and isolate this noise.

Not until a rash of negative comments about folks unable to hear this noise did it become obvious to me my mistake. Ears were placed next to tweeters with and without their DACs connected to USB without any additional noise.

Fraud!

My broad use of the term noise could easily be thought to meant audible noise: noise in the range of human hearing.

Noise that impacts sound quality on USB is, of course, outside the range of human hearing. It's in the megahertz region where computers are most active: side effects of high speed number crunching.

I am certain most of my readers understand this but—and it is my bad—I need to be a bit more careful throwing about words that have many meanings.

Otherwise, that which I am trying to communicate will get its wires crossed.

Your moving system into the dedicated room is huge improvement by it self.As someone posted it will be even more evident making cables changes.Maybe not at first but as things settle and your ears hear the change’s that youve made.

I just changed out all name brand made cable for my diy/parts wires and went with no shielding (alpha 3) on amp and conditioner...just cd player that is plugged into simple shunyata hydra 4 is shielded.Its been a learning experience and to my ears connectors along with conditioner cable seem to make biggest impact.It providing feed for upstream.

@thyname   It's interesting he mentions "galvanically isolated" for DAC's to "clean up  and isolate noise", since doing so introduces a transformer or capacitor in the USB chain, which can change the phase of the signal.  But it hardly matters because this is the analog side of the signal, which is not used directly by the DAC. 

Finally, all but the cheapest USB hubs are already "galvanically isolated" to ensure an accurate clock signal on the downstream USB ports, so I'm not sure where's he's going with the entire message.

@tomrk : If you want to question stuff, please feel free to do so directly with the manufacturer, or get an engineering degree. I have no horse on this race, as I don’t own any PS Audio pieces at this time, nor do I intend to buy one anytime soon. I brought it up simply to illustrate the concept of “noise” in the context of audible buzz, hum, etc.

It’s a bit of stretch to say all USB hubs are already galvanically isolated, but I will not entertain your questioning of this, simply because I don’t have time I can waste. Apologies in advance 

@thyname  "or get an engineering degree"

Already done.

"It’s a bit of stretch to say all USB hubs are already galvanically isolated"

I didn't say all,   But no doubt some manufacturers will put their name on an average USB hub, put a nicer case on it and sell it for a lot of money to convince you it has some advantage over the ones you can buy for $30.