110 -> 240 step down converter

Hi. Your question is confusing. What you need is a wall mounted power adapter transformer, from your

230VAC net to 9VAC, capable of 500mA or 5VA, with the same size plug, for sure available at many places at your location. And nothing else. No 110-->240 nor 240-->110 anything to keep things simple. Choosing any of your 24VA or 65VA mentioned transformers will be more expensive. Miguel
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Externet
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i don't see any reason why you can not simply go to your local radio shaft or hardware store and get a wall wart designed for your 240 system down to 9 vac? in any case the first one should work find.

Beeble wrote:

Reply to
Jamie

apologies if this is the wrong group for this question.

i live in australia and i'm looking to import a soundcard from the US that comes with an AC powered breakout box. it's described as:

"9v AC 500 mA 'wall wart' power supply"

i'm a little confused as the step down converters aren't described as having similar stats. two that i imagine must be able to do the trick (based on their price) are described as:

240v-115v (24VA) -
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and

240v-115v (65VA) -
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i'm hoping that first one (24VA) would do the trick.. although i'm not even sure if these will be sufficient. i really have no clue

any advice appreciated. thanks

Reply to
Beeble

i initially thought that's all i'd have to do, but after doing some searching i found a lot of people in a similar situation talking about converters so it made me think that perhaps there were some internal electronics in the breakout unit that would require 110v. obviously, i am totally clueless about these things.

thanks for the info.

Reply to
Beeble

VA is a way of saying 'Watts' (roughly - I think there's some subtle difference in the way its used).

9 volts at 500mA is 4.5 watts power output from the wall wart. Allow 50% efficiency (probably better than that), and it's going to be taking no more than 9 watts. So either of them should do.

The only problem might be the supply frequency - someone posted a week or so ago saying that running transformers on a different frequency to the one they were designed for can make the magnetic core saturate. If this is right, I would appreciate an explanation as well, because I don't understand this bit.

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Reply to
andy

that

---------------------- There is a relationship between voltage and maximum flux density. For a sinusoidal voltage Vac =4.44(frequency)(core area)(turns)(flux density). The magnetising current is whatever is needed to reach the resultant flux density. A device designed for 100V at 60 Hz will be designed so that the flux density is just at or below the knee of the saturation curve of the core. If the voltage is too high, the core saturates and there will be a high magnetising current (change from being a small fraction of the total current to being larger than the load current is possible)-extra heating and possible funny smells and waveforms. Cheap devices don't allow much slack for this. Now if the frequency is changed to 50Hz, as the core and turns are fixed, at

120V the peak flux will be 1.2 times what it was at 60Hz- roughly equivalent to running the device at 144V, 60Hz.. Not good. 100V,50Hz is OK. Also a 50Hz device on 60 Hz will not run into this problem.
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Don Kelly
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Don Kelly

that

Buy a 9VAC 500mA supply locally.(Jaycar .Tricky Dicky etc.) It will take 240 volts input, have the correct plug and be approved and be cheaper. Much better than trying to use 2 transformers, 1 to get 110 volts and then 1 to get 9 volts.

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John G

Wot's Your Real Problem?
Reply to
John G

and

and

You told us it runs from a 9VAC from a wall wart, then it runs on 9 volts with no 110 volts inside it. Whatever you do you will get 50HZ and not 60HZ unless you spend heaps on an inverter converter of some sort. I silll think my original suggestion is the easiest.

Anyway what is a Breakout Unit? So we might have some idea what we are advising about .

By the way I have worked in electronics service in various fields for 50 years in Australia and this 120v/60hz american thing has been a PITA for ever.

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John G

Wot's Your Real Problem?
Reply to
John G

It's basically just an external controller box for an internal soundcard. It sits outside your PC connected to your soundcard and you can run cables (guitar, microphone, etc) in and out of it.

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That's the specific unit.

Reply to
Beeble

The point being that

- it's easier to plug cables in and out of

- if it's well designed, there's less problem with EM interference with the analog signal before it's digitised.

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Reply to
andy

heaps on

are

Yes I still think a local wall wart is the way to go. The american one will not be approved for use in Aus any way.

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John G

Wot's Your Real Problem?
Reply to
John G

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