AC Dedicated Line

Good catch! What is the music signal? That’s what I’d like to know about. 

Some valid and some not so valid points on this subject.  
The amperage of a circuit breaker has several requirements.  Example: a 15 amp breaker should have the correct wire distribution...not to exceed the capability of the breaker....this should be 14 gauge 2 conductor + ground.  A 20 amp circuit should be a 20 amp breaker with 12 gauge 2 conductor + ground.  Exceeding the recommended wire gauge for a specific amperage breaker is just plain dangerous.
Attempting to wire 3 separate circuits to your hi-fi room to 3 separate outlets is a terrible waste of $$ and you will absolutely assure yourself of a serious ground loop & concomitant noise/hum.
Go ahead and bring in 1 dedicated 20 amp circuit to a good quality duplex (2 plugs like most household outlets) outlet.  
Many people are under the misconception that the electrical ground for your home/apartment/domicile (in the foregoing referred to as home) is provided by your electric company.  Very false.  The ground is a true earth ground made by the electrician that wired your home.  It is a 6' copper rod driven in the ground and connected to your electrical panel with a large single conductor to the ground bar in your service panel.
All of your grounds go to that ground bar in your service panel.
The only wires that your electric company brings into your service panel are the supply or positive wires (2) and a single common conductor.  
The 2 separate supply wires are 120 V and supply the 2 supply bars of your service panel and the single common conductor go to the 2 common bars of your service panel.
The breaker fits over the supply bar and common bar to make a circuit breaker perform. 
The best arrangement is to purchase a hi-quality (example: Furman) 15 amp power strip.  You can spend additional $$ for a power conditioner or the like but I would recommend just using the power strip first.

Best

Exceeding the recommended wire gauge for a specific amperage breaker is just plain dangerous.

To be clear, I assume you are saying that what is dangerous is using a wire gauge number that is higher than the gauge number that is normally specified for use with a breaker of a given current rating. Using a gauge having a larger diameter (i.e., a lower gauge number) than what is normally specified would not be dangerous, although as Ieales has pointed out doing so is unlikely to be beneficial.

Although your use of the phrase "the correct wire distribution...not to exceed the capability of the breaker" leads me to wonder if my assumption about the meaning of your statement is correct.  And if you are saying that using a heavier gauge (a lower gauge number) than what is normally specified for use with a given breaker is dangerous, I would have to disagree.

Regards,
-- Al

perazzi28

A 20 amp circuit should be a 20 amp breaker with 12 gauge 2 conductor + ground.

Not necessarily - it depends in part on the distance between the panel and the outlet. Always check NEC and your local authority.

Exceeding the recommended wire gauge for a specific amperage breaker is just plain dangerous.

It isn’t clear what you mean here, as Al has already noted. It is absolutely safe to use a thicker wire than is required by code.

Attempting to wire 3 separate circuits to your hi-fi room to 3 separate outlets is a terrible waste of $$ and you will absolutely assure yourself of a serious ground loop & concomitant noise/hum.

Hmmmm, not in my system. Just the opposite!

Many people are under the misconception that the electrical ground for your home/apartment/domicile (in the foregoing referred to as home) is provided by your electric company. Very false. The ground is a true earth ground made by the electrician that wired your home. It is a 6’ copper rod driven in the ground and connected to your electrical panel with a large single conductor to the ground bar in your service panel.

You are mistaken. Electricity flows back to the source. The grounding rods are safety grounds.

All of your grounds go to that ground bar in your service panel.

That’s true.

The ground is a true earth ground made by the electrician that wired your home. It is a 6' copper rod driven in the ground and connected to your electrical panel with a large single conductor to the ground bar in your service panel.

Very False.

Many locales permit Ufer grounding.
https://en.wikipedia.org/wiki/Ufer_ground and https://www.ecmag.com/section/codes-standards/what-ufer-ground-concrete-encased-grounding-electrodes

Ufer efficacy, like most things audio, is contentious. Concrete resistivity varies dramatically [≈10^4]. Factor in construction vagaries, rebar fabrication code compliance, local soil and the likelihood of two installation being identical is slim.

Any ground rod MUST tie to the panel neutral. Any circuits that have the safety ground connected to 'earth rod' only are illegal and dangerous. The earth [dirt] is high impedance and insufficient breaker trip current will flow when an equipment fault makes the chassis live.

How many 'AC Dedicated Lines' are actually worse from using incorrect safety grounds and steel conduit and random wrap individual LNE than the plain old Romex it replaced?