So here is the potential issue, which is three fold:
1) While your prior line was not dedicated, per se, it may have been dedicated uninitentially. If almost nothing other than a few light bulbs were utilizing that line, then it was virtually a dedicated line to start with, aside from splices, which do have a minor effect of their own, especially once you multiply the in line quantity of splices. Yet, if your equipment was plugged into the first junction of the entire circuit (where the homerun cable splices in), the follow on splices would have no effect on the purity of signal to your equipment....only the draw of the minor lights plugged into those follow on receptacles would have an effect....which again, is miniscule if talking 50-200w without motors or compressors or heating coils involved. Therefore, in that scenario, there would be no, or almost no improvement in the new dedicated line.
Improvement with a new dedicated line would only come if one or more of the following were true of the prior, non-dedicated line:
(a) The prior line ran directly along other electrical lines, causing magnetic interference.
(b) The prior line ran in the wall directly behind items such as an a/c unit, refridgerator, or electric oven/microwave...hi magnetic field appliances
(c) a somewhat hi current draw item, or item with a coil (magnetic influence throughout the circuit), was running in that same cirucuit, ie, fan, hair dryers, electric appliances, televisions, etc.
(c) The prior circuit was very old....say about 20 yrs +, thus had oxidized splices and receptacle connections feeding the rest of the line (again … less impactful if the receptacle outlet your equipment used was the first in the line where the homerun was present)
If none of the above was true of your prior line, then the new dedicated line will not necessarily show any improvement. Though, your use of 10 AWG will eventually have a benefit of its own...here-follows:
2) Yes, the wire needs to burn in...its a brand new line of #2 Copper, which isn’t even OFC (oxygen free copper). The level of impurities is high compared to OFC, and the number of molecular barrier points for the electrons to make their way through is, if I recall correctly, 100x greater than in standard 99.9% OFC (can’t remember exactly how much higher,,,but it is significant...wouldn’t mind someone fact checking the actual increase on that). So, burn in for an in-home Romex/NMB cable takes considerably longer than with any of todays audio cables, or audio grade power cords. Throw in that it is 10 AWG,,,,which you are highly underutilizing, and that’s a whole lot of electron aligning that has to be forced to occur before audio quality is restored. What your equipment is receiving is the extreme electron flow limitation of a new Romex cable which is an extreme size at 10 AWG.
Give it time ,,, it will happen ,,,, could be 400-600 hours of use.
3) On a final note, please please please switch that 30 amp breaker to a 20 amp. It will not impact your sound quality in a significant manner...the eventual benefit of the 10AWG wire (once burned in) will be greater than the minor limitation of the 20 amp breaker. So your choice of in wall wire will still be of benefit, and not a waste of your time and money.
Take a look at the total draw of your plugged in equipment ,,, if it is 20 amp or higher, eventually that receptacle will break down, and begin to fall apart internally as the plastics/pvc/etc harden to a brittle state. As those materials slowly break down, miniscule electrical arcing will begin to occur, eventually building to an audible hum (if you’re lucky). This would be quite detrimental too all of that expensive gear plugged into it, before you ever hear the hum.
Even if you are not at or near that 20 amp of draw, eventually, someone else will own that home and they will have no clue if they are overtaxing the receptacle because the breaker won’t trip, and that’s where the receptacle could actually reach a point of extreme heating. Receptacles are rated at 80% of the level they are considered to be 100% safe to. Thus that 20A receptacle is designed to be 100% safe up to 25 amps. At 25 amps it will get quite warm, quite quickly. Everything above that amperage will increase the heat build up exponentially and very quickly, and literally could make the receptacle melt, cause shorts, and catch fire. Honestly, I’m not being an over zealous safety freak … these are real scenarios that can and will occur if that receptacle is loaded to hi.
