Dedicated lines — how many? Other advice?

That is the whole point of the test. To educate yourself and your ears to actually maybe understand what everyone else is merely talking about. The fact of the matter is until you have actually done this stuff you just don’t know....It is nice to cut and paste stuff others have done. Do you see the difference between cut and past and knowing from experience?

To "maybe understand." Thanks so much.

So "maybe" you can understand that you’re not the only one who listens or tries things. I do know the difference. So do others. And I am not disputing your (insultingly simple) advice to try things and listen.

But bear in mind that you gave an instant and fairly definitive answer -- one dedicated line, no surge suppressor. That instant answer to my question shows what’s worked for you. But by researching what others have found -- relayed, I admit, via the vaunted "cut and paste" method -- what do we discover? Oh, that there are others beside you who have as much experience and acumen as you do (can you, maybe, understand that is possible?). Lo and behold! They, too, have also listened and tested -- and look! they found that *more* than one dedicated line was better. And they found that ground loops are not the best rationale for going with only one dedicated line to the exclusion of more. At least, you know, until there’s a chance to listen.

You see the difference? You see why it is possible to learn so much from seemingly simple research like looking what other testimony report? It is nice to dismiss stuff others have done. Do you see the difference between entertaining there are other points of view besides yours and simply promoting your experience as if it was universal truth? I’m hoping that maybe you can understand the difference, but I won’t be betting much on it.

Once again, I invite you to throw up your hands and say "Oh well" and stop (again) polluting my OP's with your snide remarks. You don't like me, you don't respect me, and I would rather forego your advice (and yet another invitation to genuflect at your system) than be exposed to your toxic personality. Begone.

@hilde45,
Run a 10/awg BX/MC cable solid core conductors from the breaker panel to a metal receptacle box. The metal sheathing on the BX/MC cable absorbs the (EF)) electric fields emitted by the wires and shunts it to ground. Now from panel to plug is shielded. The upside is low line noise and reduced antenna effect. Downside BX/MC cable is pricier. Run at least two dedicated 20 amp lines for audio. I have four in my audio rig. No ground loops See the links below. Hope that helps. Mike.                                                                                                                                 https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

 https://healthybuildingscience.com/2013/01/15/residential-wiring-best/#:

Myself has a electrician audio friend install 2-20 amp circuits 
to low resistance ,and isolate I had Awg 10 wire , Pangea to HD 
Solid Copper Gold plated AC outlets they are very good ,
the lines are 4 wire ,have 2 grounds ,1 common ground , the other 
is a insulated Isolated ground , it made a tremendous difference .
I had stock awg 14 originally the noise floor is dramatically lowered 
also the 20 amp circuit breakers are Silver and were $60 each but well worth it ,he had to order them for these are only use in critical 
installs he said and I had installer a Siemens big surge suppressor 
installed at the breaker box to protect it.

@ditusa @audioman58  Thanks -- taking notes and following those links. Appreciate the actual help.

Glad to help , happy 4th to all 🇺🇸