AC Dedicated Line

millercarbon

Its a common misconception, that the big benefit of the dedicated line is current. It sure does not seem that way to me.

I have found it to be a major benefit, but I have a complex biamplified system with big amplifiers.

Originally ... my room was a normal 15A circuit. Normal in gauge. Normal in the circuit running from outlet to outlet, four or five of them, including lights, with my system outlet sort of in the middle of this mess. When I replaced this with one wire run directly to the one system outlet the improvement was huge, obvious, unambiguous. Even though it was the same breaker, same wire. Only thing different, one continuous wire not going outlet to outlet with multiple connections at each.

Yup, I'm not surprised that resulted in improvement. Tight, direct connections; simple, direct grounds; those things make a big difference.

Next I replaced the normal gauge (10/2 I think, whatever) with overkill 4 ga.

Whoa, 4AWG! That's huge, and difficult to install. For a 20A line, 8 or 10 AWG should be fine and is still way beyond code.

Yes it would be hard the normal way, pulled through holes drilled in studs. Would also use more wire. Mine is hung under the floor in almost a straight line and through just two holes, one at either end. 

Current definitely does drop with load. I don't deny it. Why? All you have to do is watch the light dim when you turn a blow drier on to know there's a drop with load. The question is, does it then sound better to use thicker wire to get more current? Sure didn't sound like it to me. I mean it did sound better. Just not anywhere near what you'd think for such a huge increase in gauge.

ieales

Not so. Full current is supplied by the PSU caps.

You’re either deliberately splitting hairs here, or just not reading carefully. Obviously, the PSU caps can’t supply current to components not connected to it, but which are connected to other dedicated lines and power supplies. Those components are indeed powered by their individual caps which are charged by ... the line. They can’t be charged by the line if it has run out of current - hence the advantage of dedicated lines. (And a reason to not power all components from the same leg - but that’s a separate and debatable issue.)

If the line has run out of current, the breaker has tripped. AGAIN, cap charging is almost completely asynchronous to the music. 

In the studio, we had a stack 4 of Bryston 3B for the tri-amped mains. Dual woofer, 1 mid & 1 tweet. 8 amplifiers. All on one 20A circuit. In LA, we had frequent brownouts and full outs. When power was restored, EVERYTHING came on at once. If the breaker doesn't blow when powering them all on at the same time, the line can handle the load.

In round numbers:
A 200W amplifier supply is 40V, 8 200w amplifiers could supply 40A TOTAL into 8Ω. On 120V, that is a 3:1 transformer turns ratio. So a 20A circuit could supply ≈120A to the amplifiers. Add in the FACT that a 20A breaker can supply peaks of several times 20A. A Class B resistive breaker has a 3-5x multiple of rated capacity for a couple of seconds. THAT'S 500A IN THE AMPLIFIER!!! See  https://www.c3controls.com/blog/understanding-trip-curves/ 

The advantage of one circuit is earth reference with improperly designed gear, which IMO is far more prevalent in HiFi that properly designed. Balanced gear can have some immunity, but unbalanced could be a nightmare on multiple circuits.

And for the 999th time, the power loss, even at worst case conditions is under 1db. For that loss to occur, the peak must be in sync with the line frequency.