In wall AC cables

erik_squires

Honestly the normally recommended sizes is best. Having too low an impedance will encourage more noise going back and forth in the wires ... To get uber-fancy run a 220V 60 AMP line and dedicate 220->120 V transformers in the room.

Using "recommended sizes," or using the minimum gauge to meet code, is often not the best approach. By de-rating the wire, you'll reduce or eliminate voltage drop and improve the quality of your ground connection. That can yield greatly improved results. Using minimum wire gauge as a way to reduce noise is introducing a remedy that may be as bad or worse than the disease.

As far as I know, a 220V line is not an option for residential use in the US. Erik may have meant to suggest 240V, but you'll absolutely want to check with local officials before considering that - I think it may be against code in some locations. If you want to install isolation xformers, one option is to keep them out of the room and install them at or near the service panel.

I ran 3 lines. One for amp, one for pre and TT, one for digital sources. Used 10ga romex. 

There are other safety issues involved with overrating cables in that they may increase the minimum break current of circuit breakers.

Voltage drop should be negligible.

Now I think you misunderstood. First, 220V = 240V, really just about the same thing here. It will probably measure closer to 240 but we call it 220.  Second, residential service in the US usually IS 220 with a center tap, which gives the nominal 110V (Again, closer to 120V, it's just what we call it).  220 Service is often used for electric ranges, air conditioners, etc.

Secondly, I wasn't recommending he use 220 outlets, but that he run 220 service to a transformer ($200 - $500 ish) professionally installed in the room. This would give the least voltage drop and highest noise rejection possible.

None are really my preference, but if you want to get that fancy with room electricity that's my suggestion.

YMMV.

Best,


Erik

erik_squire

There are other safety issues involved with overrating cables in that they may increase the minimum break current of circuit breakers.

It's not "over-rating," it's "de-rating," and perfectly within code. A 20A breaker should trip at the same current regardless of the gauge wire to which it is connected. That's why it's perfectly within code to connect 8 ga or 10 ga wire to a 20A breaker.

Voltage drop should be negligible.

Yes, with de-rated cable, voltage drop should be negligible. What you call "normally recommended sizes" can often result in voltage drop. It's measurable.

I wasn't recommending he use 220 outlets, but that he run 220 service to a transformer ($200 - $500 ish) professionally installed in the room.

Again, I'm pretty sure that isn't always allowed under code, at least in the US.

@cleeds

What exactly do you think is not allowed? 220V is an uncommon, but not illegal outlet type.

Circuit breakers are rated for current in two ways. What current they trip at (15A, 20A, etc.) and the maximum current which they can interrupt, called "Interrupt Rating." That is, if a short occurs, how much current could the breaker interrupt safely. This must take into account the size of the wiring and the transformer type all the way back to the transformer. However, usually this is taken care of by the panel or service breaker, and not the individual breakers themselves.

So, increasing the gauge of the cable used at the service entrance may in fact result in having to change the service or main breakers to have a greater interrupt rating, even if the trip current rating is the same.

Best,


Erik