Dedicated Line Advise


I currently have a 20 amp dedicated line run to my small HiFi rig; amp, preamp, CDP, TT, power conditioning. I wish to add a second line using the same electrician who has worked on my house. It looks like he used 12 gauge Romex last time.

What are the key facts that I should know in case he is not familiar with doing wiring for audio systems?
I'm talking about the installation at the breaker box, e.g., keeping proper phase and preventing a ground-loop between the 2 circuits.
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Any qualified electrician will wire it to code in and out of the box. It is the same for audio applications as any other outlet.  AFAIK ground loops are negated by properly grounding each line, at least that's what I've been told.  
Nothing special involved. I put two dedicated lines in myself. Very easy to do. I also used 12awg Romex. If you are not familiar with electrical wiring, get the electrician you used before to run another.
I believe you would want both lines on the same phase within the box. I would use one for digital and one for analog. Would you consider adding 2 additional lines? One could be dedicated to amplifier.  
When you say use the same phase, does that mean phase = leg. Use the same leg?

I see that audio AC line 1 is installed on left side of circuit box, which is now full. As long as he puts line 2 on the right side of box, same phase, then everything is cool. Is that correct?

Also, previous owner installed 220v furnace on left side and 220v dryer on right side. Am I in good shape for this install? Thanks.