If I install '20A dedicated circuit'

Can't hurt to have both, IMO.

The insidious thing about "dirty" power, at least in my experience, is you don't know you have dirty power until after it's been conditioned. Elements of dirty power...edge, grain and hash in the music...can't necessarily be heard, but are more often felt. Sometimes the presence of these elements just makes me feel uncomfortable, and make me want to leave the room. The effect of dirty power is almost subliminal, and can be analogous to working in flourescent lighting versus incandescent lighting...if that makes any sense

Why? Because dirty power can't always be heard as clearly as its absence can be experienced. It's hard to "hear" clean power because it's like trying to listen for something that isn't there, but clean power can be attributed to a blackness in the sound, and the ability of the listener to relax and settle in with the music.

The only way to experience this is to experiment with power conditioning products by installing them and living with them in the system for a few days before taking them out.

I have often found quick A/B'ing of power products to be inconclusive.

As others have said, it depends. In my weekend system, I have two dedicated 20A lines but they still vary in voltage more than I like. I use an AVR and filter.

Kal

That is not necessarily the case as someone mentioned it depends on the quality of power comming into your panel. I used a passive conditioner on and off for about 12 months. I did not like it, system sounded veilled, so I sold it and I plug my equipment directly into the wall. A dedicated circuit is still a good idea; I installed one but can't say I heard any real sonic benefits.

Chuck

I installed 3 dedicated 30 amp circuits 1 for each amp and one for the source componets. It is the best thing I ever did for my system. I don't use anything between my componets and the wall because I it would have to be all 10 gage wire and not restrict the current in anyway.

Mark

what you are looking for is something that will eliminate voltage swings. the house voltage will be the same during the day as night. get a exactpower EP15A. i just put one in my system. all i can say is WOOOW !!!! there is two for sale as i post this on audiogon. they are $2500.00 new. there is a asking price of under $1200.00 in either silver or black. get one. no negatives like some power conditioners can have. most of these products induce noise into the system. this is what is making my system sound so much better. no voltage swings and less noise.the voltage stays at 120Vrms. no power conditioners needed as well. big improvement in sound. what TVAD is saying is how to describe what the EP15A does.
bill