[jules]

Hi all,

Since we didn't quite get off the ground with the age old challenge of which way water spins while going down the plug hole, can I raise an issue that might be more relevant to audio:

In one sense it shouldn't matter if our mains supplies are 240V AC,230V AC, 120V AC or 110V AC. Transformers in our systems faithfully give us whatever output we need but is it possible that different supply voltages are not, before or after transformation, equal?

There are some clear, simple differences. For a given cross section of wire, 240V will have half [well, very close to] the resistance of 110V. I presume that wiring standards take this into account but at the same time, if the wiring of a house [or apartments!] is near its limits, perhaps 240V has an advantage?

Similarly, where pugs/sockets and other connections are involved, the surface area of good contact becomes less critical. Are the connectors/plugs used in 110V systems actually twice as good as those used in 110V systems?

Finally, where long runs of wire are involved, 240V could have the advantage of less voltage drop.

Does 240V kill you in a faster and less excruciating way if you get it badly wrong?

It might be that National power standards and local power generation quality are far more important factors than the above challenges but it would be particularly interesting to hear from from people who have listened to systems in different countries with different voltages, to see if there's any trends apparent. I don't see this question being answered by speculation or theoretical discussion as there's so many variables involved but the weight of combined experience could be useful.

Jules







 

[Wayner]

Sorry, but your first assumption is not correct. The wire size for 120 or 240 volt is close to the same gauge. remember, as voltage goes up, amperage goes down. Watts (P) divided by Volts (E) gives you Amperage (I) and amperage is what the wire gauge and circuit breaker are based on. Besides, the value of resistance is so tiny, that is doesn't really matter.

Wayner 

[jules]

Wayner,

we're both working from the same formula here, V=IR. Yes, as voltage goes up current comes down and that is simply another way of re-stating what I said above.

For an amp/system that uses a given current [at its own working voltage], the current drawn on 240V will be half that drawn on 110V. If you take an example where the resistance of the wire is 2 ohm and the current drawn at 240V is 2.5 amp, the current drawn at 110V will be 5 amp, the voltage drop is thus:

for 240V, drop Vx = 2.5 X 2 which is 5V
for 110V, drop Vy = 5 X 2 which is 10V

[These calcs are not exactly the same for AC supplies but the variance does not change the results significantly.]

you could well be right in that resistance might be "so tiny it doesn't matter" for the most part, though the point remains that any given resistance will be twice as detrimental to a 110V system as it will to a 240V system. If the resistance of home wiring is only in small fractions of an ohm, it's only going to produce losses of a few volts and I really don't know at what point it starts to matter with audio equipment. I know from experience with power tools that a voltage drop of 10V makes a big impression on the output but maybe you can tell me what it takes to mess with the performance of amps and other audio gear?

Jules

[bluesky]

Hi Jules

I am just revisiting this post from ages ago.  One thing I did think was that voltages vary so much from house to house and other factors.  My voltage is (usually) spot on 240V although we have shifted to nominally 230V and a good friend of mine has 250V in his home as he is right beside a transformer (the big kind).

I mention this as a way of saying that the resistance factor is small fry compared to such variable mains voltages, which is my case also varies according to the time of day, it is higher at night when there is a less base load on the system.  I have also found that the transformers we use in our amps also vary quite a bit, a nominal 12V turned out to be 13V when measured and was slightly different on each of the primary output voltages, like over 1.5V from one side to the other!

Like I said the resistance factor does seem to be small fry when compared to these variations within the mains and the output from the transformers used.  The regulation of the power supply would appear to be much more important to me at least.  It has made me realise that it is all swings and round abouts, what you lose here you pick up there and vice versa, it is not exact by any means.

I have never worked out why there are such different mains voltages but they have standardised fairly world wide at 115V and 230V now which makes it much easier for transformer manufacturers at least, as only two mains voltages are now used (for the most part).  It is quite correct that voltages can only be transformed by stepping up or stepping down and this will effect the current by a reciprocal amount but will nevertheless supply enough for our amps needs.  To my mind having a clean low noise power supply is by far the most important factor rather than a volt or two either way in output.

Cheers 

Bluesky

[Johnny2Bad]

To clarify, there are two mains frequencies worldwide: 50 and 60 cps. That is the true difference between national electrical standards.

Voltage differences are just for the internal wiring of a home or building; in North America all homes receive 240V service to the main panel, where it is then split into two 120V legs. If you want a 240V circuit in a North American home, it's trivial to provide it (the circuit breaker and outlet need be changed from a more usual 2x 120V circuit)

Furthermore, all North American homes have two 240V circuits installed as standard, in addition to the 120V home wiring circuits; one for the stove (which is 2x 120V internally; the stovetop and oven are different legs) and one provided for an electric clothes dryer.

People who want to use 240V for workshop tools, for example, will tie into the Dryer Circuit which provides 30A @ 240V.

The stove circuit is high amperage; if you install a gas stove you can then utilize this circuit for some other purpose, which offers 40A @ 240V.

Since it hasn't been mentioned yet, it is worth noting that Japan uses 100V, not 120V.

In the US you are more likely to run across utilities that provide 110V, here in Canada it's always 120V. Unloaded, my home wiring generally provides about 127V 60 Hz but this will drop to 117~122V when a load is placed on it (measured values).

[JohnR]

To clarify, there are two mains frequencies worldwide: 50 and 60 cps. That is the true difference between national electrical standards.

I think that might be a little simplistic Here in AU we have 415V (OK I suppose that is now officially 400V) three-phase power. This is not at ALL the same as two-phase. Some houses do have three-phase into them, whereas others (like mine) have only a single-phase 230V (nominal) supply.