Code in most locations will specify an "arc fault" breaker on a 20a circuit. In my rig, this has caused headaches as the breakers occasionally trip on dynamic passages. I have 2 dedicated, short run 20a feeds direct from breaker box at service entrance, feeding system with McIntosh MC462 and MC257 power amps and multiple powered subs.
What type of wire for dedicated 20A AC lines?
I’m about to have two 20A dedicated lines installed. What type of wire should I use? I know there are differences of opinion on whether to use 10 AWG or 12 AWG, however the link below makes a great case for using even 8 AWG solid core copper on longer runs like mine will be (50 ft), to ensure a lower resistance, lower voltage drop over the long run, and therefore more access to instantaneous current for my Gryphon Diablo 300. The wire would need to be stepped down to 10 AWG to connect with the receptacle. The article actually states that the thickness of the wire is more important than the fact that it is dedicated…
Assuming I want to follow this advice, which again makes sense to me, where would I find such wire to give to my electrician?
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An Overview of Audio System Grounding and InterfacingTake note of page 16. Read pages 31 thru 36. Note the chart on page 35. AL armored MC measured the second best. Number one being the best where the hot and neutral conductors are twisted together the entire length of the branch circuit. The EGC is ran along side the twisted pair. . |
Someone earlier mentioned mains feed heat buildup. So I measure it. My system is 715 wpc fed from a single 20A /12ga cct. Three bottle rocket amps account for 25% of the power, so average draw is larger than if all SS. Class A would be worse, but Class A power transformers negate the issue as we shall see. After three hours of robust pop program, temperature rise on the 12ga cct was 2.9°C measured inside the yellow sheath with a T thermcouple. The really bad news is that over the 20 foot run, the resistance increase is a whopping 51mΩ or 0.051Ω for the non-technical types. This is added to the 20°C value of 32mΩ. The good news is the power transformer internal resistance also rises 1 - 2% or much more than the line feeding it. Calculated improvement in self-heating for 10ga is about 30mΩ, less than the PT and less than the connections from the power line to the transformer winding! For those posting fancy graphs of diode current, those are steady state loads. Music current draw bears no relation to those graphs. Spend all the money you want on overkill wiring. It will do no more for the sonics than a fancy faceplate or blue LEDs. Sonic improvements can be achieved by ensuring that all connections from the utility input to amplifiers are pristine. Inspect and cycle all power plugs every six months. |
FWIW, the 10 gauge dedicated orange romex line purchased at Home Depot and run from a 20 amp breaker to a 20 amp medical grade outlet sounds better with my gear plugged into it than the 12 gauge non-dedicated line right next to it on the wall with a "deluxe" but non-medical grade outlet. The difference is not subtle. I plug my amp directly into the green dot outlet, all other gear goes through the same outlet via a power conditioner. If I had not installed the 10 gauge line while I had the wall open, I would have always wondered if I had made a mistake. Now, in practice I have absolutely no regrets, although in theory some of you apparently believe I should be sad I spent the extra money and wrestled the stiffer wire. YMMV. kn |
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