# 110 -> 240 step down converter

B

#### Beeble

Jan 1, 1970
0
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) - http://tinyurl.com/6pvd9

and

240v-115v (65VA) - http://tinyurl.com/4q9uf

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

J

#### John G

Jan 1, 1970
0
Beeble said:
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) - http://tinyurl.com/6pvd9

and

240v-115v (65VA) - http://tinyurl.com/4q9uf

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

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.

A

#### andy

Jan 1, 1970
0
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) - http://tinyurl.com/6pvd9

and

240v-115v (65VA) - http://tinyurl.com/4q9uf

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

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.

B

#### Beeble

Jan 1, 1970
0
John G said:
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.

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.

E

#### Externet

Jan 1, 1970
0
Hi.
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

J

#### Jamie

Jan 1, 1970
0
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.

D

#### Don Kelly

Jan 1, 1970
0
andy said:
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.
----------------------
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.
--
Don Kelly
[email protected]
--
http://www.niftybits.ukfsn.org/

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J

#### John G

Jan 1, 1970
0
Beeble said:
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.

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

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.

B

#### Beeble

Jan 1, 1970
0
John G said:
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

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.

http://www.m-audio.com/products/en_us/OmniStudio-main.html

That's the specific unit.

A

#### andy

Jan 1, 1970
0
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.

http://www.m-audio.com/products/en_us/OmniStudio-main.html

That's the specific unit.

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.

J

#### John G

Jan 1, 1970
0
Beeble said:
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.

http://www.m-audio.com/products/en_us/OmniStudio-main.html

That's the specific unit.

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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