advice on dedicated line

One big thing is all of the circuits need to be on the SAME LEG.
Which means they all come from the same 'half' of the 230volt pair of 120 volts parts.
So you don not want one line to be say from leg A and one from leg B, where A and B add up to 239 volts.
All the outlets need to be from one leg. So they never can 'add together' to make 230, but only 120 volts.
And then the outlets need great grounding. You WILL have hum issues if the electrician messes up the grounding.
So remind him at teh start tath grounding has to be done right (gauranteed no hum)
Plenty of folks cry about serious hum problems AFTER THE FACT.. due to the electrician not understanding the basic importance of proper grounding as all three will be interconnected by equipment.

"Do I want two dedicated lines--one for the amplifier and one for everything else? So 2 20 amp circuits with 10 gauge wire?"

If you have a small system and as long as your amp is not a monster, you can get by with 2 dedicated 20 amp lines. The current draw from a CDP, DAC, Sonos, or preamp is very low. Good outlets are important and so is surge protection. Later on, you'll probably want to get a power conditioner.

Thanks, all. This is very helpful. My amp is 50wpc, so I am thinking 2 lines. Lowrider57 (or anyone else who cares to answer): would I get a separate surge protector for each outlet, and can you recommend a good, moderately priced one? Also any more suggestions for good outlets? Elizabeth, I have another question on ground wires, but that will have to wait a bit because I am heading out now to go audition some speakers. :). Thanks again, everyone, for your excellent guidance. M.

Lak has it covered nicely.
The only add I would offer is that if your system is quite a distance from your service box, you may consider having them run a 50 or 60 amp sub-panel, positioned somewhere nearer to your system and then all your individual circuits would run out of the sub-panel.

Good comments by the others. I agree that two lines should be adequate for your relatively low powered system. I would add that experimentation with what components are plugged into which line could very well be worthwhile. And it is even conceivable that you could find that best results are obtained with the entire system connected to just one of the dedicated lines.

I say that because while on the one hand connecting power amplifiers and digital components to a separate line from the one powering components that generate or process low level analog signals can minimize coupling of electrical noise from the former to the latter, a tradeoff may come into play, depending on various factors such as the internal grounding configuration of the specific components. The tradeoff being the possibility of increased susceptibility to ground loop issues, especially if the connections between components that are on different dedicated lines are single-ended (utilizing RCA connectors) as opposed to balanced (utilizing XLR connectors).

If those interconnections involve analog signals, the symptoms of ground loop issues would be either low frequency hum or high frequency buzz, or both. If those interconnections involve digital signals, the symptoms would be more difficult to predict or identify, but may involve a general reduction in clarity, to an unpredictable degree.

As far as surge suppressors are concerned, for optimal protection you should have one for each dedicated line. Again there is a possible tradeoff, however, as some people find that sonics benefit from having their power amplifier plugged directly into the wall, with no surge protection or power conditioning.

I and a number of other members use this $259 8-outlet BrickWall surge suppressor/line filter with excellent results. Note that it provides some degree of noise filtering between each of its four duplex outlets, as well as between those outlets and the incoming AC.

Best regards,
-- Al