Lets talk dedicated lines

It seems to me that the first thing you should do before incorporating any of the good suggestions mentioned above is determine if you really have a problem that needs fixing. If you do not hear any hum, noise, hash, RFI or other anomalies during silent passages or with the volume turned up without a signal, spending the money on dedicated lines, power conditioners, regenerators, etc are all solutions to a problem you don't have. 
J.Chip

It seems to me that the first thing you should do before incorporating any of the good suggestions mentioned above is determine if you really have a problem that needs fixing. If you do not hear any hum, noise, hash, RFI or other anomalies during silent passages or with the volume turned up without a signal, spending the money on dedicated lines, power conditioners, regenerators, etc are all solutions to a problem you don't have.

Good advice. Well... one problem. Your RFI has to be pretty awfully bad to be heard like that. Not that it can't happen. But that's a pretty low bar. We can do better. 

Once again: 

RFI is radio frequency interference. Radio frequencies are everywhere. When they cross a wire, any wire- every wire- they induce a current in that wire. All our power comes to us via wires. Therefore, as a matter of pure irrefutable logic, we all have an RFI problem.  

So the question is not if, but how bad? That one you can only answer for yourself by listening.  

Again, here's how you do it:  

Listen to some music. Flip off all non-system breakers. Listen again. The dramatic improvement is telling you the degree to which you have an RFI problem. Which you do have. Beyond a shadow of a doubt. You will hear it. *Limited time offer! You have 30 days to hear it, or your money back!

I have done a lot, yet when I repeated this test myself recently as part of a component evaluation the improvement when flipping breakers was as great as ever. Because all those wires are collecting RFI and channeling it into the system. Whether we know it or not. Whether we believe it or not. Whether we admit it or not. Its just a fact. Go and listen. You will see.

@ volumizer

I am not sure exactly what good is the testing that was done in the link you provided.
The white paper did not address anything about a voltage that may/will be induced onto the equipment grounding conductor using the 12/3 with ground cable from the two current carrying conductors. Therein the Hot and neutral current carrying conductors. Any voltage on the equipment grounding conductor may/can cause a ground loop and hum.

It all has to do with the way the cable is designed/constructed.

Also worth noting allowing the third insulated conductor (red insulated conductor) to float above ground could have two effects. For one it may have an induced voltage placed on it from either of the hot or neutral current carrying conductors which then may induce a voltage onto the equipment grounding conductor. Second the floating above ground insulated wire may act as an antenna.

Here is a white paper from a well respected EE.
https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf
See page 16. Read pages 31 thru 36.

As for the use of a 3 wire + ground cable here is a quote from a white paper from Middle Atlantic Products. The Company is now owned by Legrand.

AC Power Wiring Types (cont’d)

Metal Clad (MC) is manufactured in both steel and aluminum with twisted conductors that help reduce AC magnetic fields. Although the steel jacket helps reduce AC magnetic fields, the twisting of conductors has the greatest effect on reducing these fields. Another benefit is the constant symmetry of the phase conductors with respect to the grounding conductor which greatly reduces voltage induction on the grounding wire. (NEC article:330)

Two conductor plus 1 ground MC (Metal Clad)is a good choice for Non-Isolated Ground A/V systems. MC cable contains a safety grounding conductor (wire). The three conductors in the MC cable (Line, Neutral and Ground) are uniformly twisted, reducing both induced voltages on the ground wire and radiated AC magnetic fields. The NEC article 250.118 (10)a prohibits the use of this cable for isolated ground circuits because the metal jacket is not considered a grounding conductor, and it is not rated for fault current.

Two Conductor plus 2 ground MC (Metal Clad)may be used in an Isolated Ground installation, because the cable contains two grounding conductors (one for safety ground and one for isolated ground). The conductors are twisted, but the average proximity of the hot conductor and the neutral conductor with respect to the isolated grounding conductor is not equal. Under load, this will induce a voltage along the length of the isolated ground wire, partially defeating the intent of isolation (see Ground Voltage Induction section of this paper)

https://info.legrandav.com/l/71782/2018-12-14/7zh25n

Note the third paragraph. Same principals would apply for 3 conductor plus ground cable.


Though the quote is for MC (Metal Clad Cable) the same tests hold true for NM sheathed cable. (Romex is a Trade Name of NM cable).


Also note the chart on page 13 for the best type of wiring and method to use.



EDIT:

For those that think they need to use an IG (Isolated Ground) type grounding duplex receptacle.

Quote from Middle Atlantic Products white paper link above.

Armor Clad for Healthcare Facilities

(AC-HCF) Aluminum Armor Clad for Healthcare Facilities (AC-HCF) is the best choice for Isolated Ground A/V systems. Like MC, it contains an additional grounding conductor, although with this type of cable it is permissible to use the metal jacket as the safety grounding conductor, as required with isolated ground installations. The biggest benefit is that the average proximity of the hot conductor and the neutral conductor with respect to the isolated equipment grounding conductor is nearly equal, virtually eliminating ground voltage induction (GVI), even on long runs.

Steel Armor Clad for Healthcare Facilities (AC-HCF) Similar to aluminum armor clad AC-HCF, but does not address ground voltage induction as effectively as aluminum(see Ground Voltage Induction section of this paper). Two other problems are that steel clad is not readily available and is cumbersome to transport and install.

.

Edit:

Like MC, it contains an additional grounding conductor, although with this type of cable it is permissible to use the metal jacket as the safety grounding conductor, as required with isolated ground installations.

Not exactly... The armor alone is not considered an effective equipment grounding conductor. There is a (bare aluminum bonding strip) that runs straight along side the three tightly spiral twisted insulated conductors.
(The white insulated neutral conductor, the green insulated equipment grounding conductor, and the black insulated Hot conductor.)


Look closely at the two pictures in the Link provided. Look for the cable with a, white, green, and black, insulated conductors. Look closely for the bare aluminum bonding strip.
http://www.afcweb.com/ac-hcf-armored-cables/hcf-lite-aluminum-health-care-facilities-cable/

Click onto "specifications" for data sheet.

Jim
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I got you beat mc. I have my own isolation transformer on the street. The electric company forced me to have that wart on my front lawn because they were worried my workshop would dim everyone else's lights. However the reverse is also true, I am isolated from everyone else. 
I have five dedicated lines all 20 amp, one to each of 4 amplifiers and the fifth for the line level equipment. There is a 6th one that goes to the projector. I do not use any special kind of outlets. All the power cords are made with hospital grade plugs from 3 conductor plus shield 14 gauge cable. The shield is floated on the equipment side. All cables and signal wiring is made to exact length.