AC Dedicated Line

You should consult or hire an electrician. If you run 3 lines of Romex 12/2, you will connect at the service panel to 3 separate circuit breakers (typically 20 amp).
Each line should have it’s own neutral and ground from wall receptacle to circuit panel. Plus this way the lines can all be wired to the same leg, or phase.

Cleeds states an important reason why you shouldn't share neutral and ground. Possible code violation and  sound quality may suffer.

Okay, actual experience here. Installed panels, drilled holes, run wires, done it all. Run my system off the conventional wiring, then ran my own dedicated line, upgraded that with a transformer, built my own- well you get it. I know what I'm talking about.

The 3 circuits you are planning are almost guaranteed to be a waste of time and money and even worse than that create more hum. Electricity always seeks the least resistance. The subs and all the rest of your system are all connected together. If it all has one ground on one circuit no problem. Using three there will be three paths to ground which almost guarantees hum.

One mistake often made is to take the wattage or amperage of each component and add them all up and assume that is how much power you need the circuit to handle. But almost never do any of them draw full power. And even less often do they draw it all at once. People think of playing full volume. When in fact the greatest power draw is usually right when first turned on. That is when the component power supply is empty and so that is when it draws full power for a second or two as the caps charge. So worst case is not blasting full power music. Worst case is having everything turned on and plugged into one switch and then you flip the switch. Even then worst that happens it trips a breaker.

Hope I made the point. You will get by just fine with one circuit. One 20A for sure. According to the interweb Argentina uses 220-240V so using a 20A with 240V is equivalent to a 40A with the 120V we have here in the States. My whole system runs on the equivalent of one 15A circuit so for sure you will be okay with 20A. 10A even should do you fine.

Whatever you decide, use whatever gauge wire and breaker Argentina code says is required for that load. 

Ideally you would run the one circuit to your system, connect a power conditioner, and plug everything into the conditioner. 

The extra dedicated earth ground may or may not help. My system uses one but it also uses a step-down transformer so its a special case. Before that when it was on a dedicated circuit, everything the same except the transformer, I used it both ways- common house ground and dedicated system ground. Never did notice the ground made any difference. It has however been reported to cause problems for some people. If it was me I would not go to the trouble unless there were ground/noise problems. Even then I would do my best to eliminate all other causes first.

So run just one circuit for your system. Then run another circuit for everything else in the room- lights, outlets, etc. As long as you are careful to make sure nothing connected to your system gets plugged into any of those outlets you should be fine.

 

With AC the neutral wire carries as much amperage as the hot wire (the current goes back and forth). You cant hook up 3 hots to one neural and expect the neutral line to carry 3X the current. And how were you planning on wiring one neutral to three different breakers?
Were you planning on using just one 4 strand romex and using 3 as hots and one as neutral. I am pretty sure that would be against all codes in any country. You would be better off installing two outlets with the 4 strand cable with one hot and one neural to every breaker.(assuming that is allowed). Two 20 amp breakers should be more than enough for any sane system. You don’t need 60 amps with incorrect wiring.

I would just add to the foregoing comments that using a single neutral run for the three dedicated lines, all of which would presumably be on a single phase in your country, would seem likely to negate whatever benefit having multiple dedicated lines might otherwise provide. As indicated in the preceding post whatever amount of current is conducted by the hot wire that is connected to a given component is also conducted by the neutral wire that is connected to that component. So commingling the AC currents drawn by all of the components in that single neutral wire would seem likely to make the three dedicated lines essentially non-dedicated in terms of any potential benefits.

Regards,
-- Al

Use a separate common for  each circuit from the receptical to the power board. You should consider a quality power condishiner.  I hooked one up to my tube amp and all the hum dissapeared without any need for extra wiring . I was going to do the same thing as you have planned. Good luck.