Test a new dedicated circuit before installing it.


So, I may take the plunge and run a 10/2 romex to my system. I'm slowly building/rebuilding my (midfi, gravitating higher) set up and sort of going backwards with first buying cables, conditioners, etc before the big components such as integrated amp or preamp.
Anyway, before installing in the wall, I wonder if I could just hook up the romex into my panel and do a quick connect since its only a 25 ft long cable I will be using anyway. I just purchased those little noise detection tools which may help see if there is any difference. I'm just trying to avoid running a circuit in the wall in a box if it ultimately won't help.

Currently I have a dedicated 20 amp 12/2 but there is more than one receptacle on it but the others are just not used. The only thing used on it is my AV setup.

Worth it? 
cissado
Nope. Not even. Worse than a waste of time, whatever you get from a noise meter (extremely questionable to begin with) becomes totally worthless when you realize a lot of the noise comes from where the wire is- and you're not testing it where its going to be!  

My system https://systems.audiogon.com/systems/8367 has been in this room nearly 30 years now. In that time its been run on a normal circuit, a direct (dedicated) circuit of 4ga wire, a direct circuit of cryogenically treated 4ga wire (yeah, I pulled the wire out and had it cryo'd!) and that's just the 120V history.

Then I got a step down transformer and so now its cryo'd 4ga 240V to the transformer. The wire since then hasn't changed but there's been a ton of improvements, the whole panel and wire being treated with TC and some other stuff. 

Each of these steps was an improvement but the biggest most cost-effective one was the first, going direct, eliminating the daisy-chain of outlets. For what you are talking about its probably worth running one dedicated line. Make sure it goes close to your system, use a Synergistic Blue or Orange outlet, and call it good. 

By the way: use your ears not a meter. Every time.
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The only benefit of 10/2 vs. 12/2 is lower voltage drop, which increases with current.

You are unlikely to notice this unless you have a long run. Certainly it won't reduce your noise.