In wall AC cables

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

erik_squires

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

It’s not the outlet that may not meet code, but your suggestion of a " 220 service to a transformer ($200 - $500 ish) professionally installed in the room." Professional installation here suggests a hardwired xformer - otherwise the user could plug it in himself - and these are governed under code. Always, always, always check local code.

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 ...

We’re not talking about the cable used at the service entrance, but the gauge of cable used in a branch circuit, and your dubious recommendation to use the minimum gauge cable.

10 gauge wire to a 20 amp breaker. Be awear that 10 gauge is a bit harder to attach to the AC outlet, but it can be done for sure.
I don't know that the brand of cable will matter.
Some audio websites sell cryogenitacilly treated copper wire if you care to spend the additional money.