John Sayers' Recording Studio Design Forum Archive

Hi,
I bought my main studio monitors from the USA and I am located in Ireland where we run @ 220v. So, I am about to buy a step down transformer and wanted to check if my setup will work as I expect it to and will of course be safe...

So what I propose to do is buy this step down autotransformer which will convert my 220v supply and output @ 110v...

http://radionics.rs-online.com/web/p/au ... D3D6D61746

On the 110v output flexible 3 core cable I propose to put a junction box where I will connect in the two power cords coming from the speakers...Each speaker draws down 200 watts making a total draw of 400 watts...

My questions...

1. Is this setup safe and is it the most efficient way to do what I need to do?

2. If so, will the 600watt auto transformer provide enough headroom for the speakers?

3. How many amps will my junction box need to be...?

4. And just to be sure, Is this setup safe?

Thanks in advance for any advise

regards hally

That is, indeed, the correct way to do it. I have stacks of equipment powered like that, through transformers. Where I live (Chile) we are also 220v / 50 Hz., so it is the only solution.

Instead of a junction box (which would also work) I use 110 v power strips (USA sockets) connected directly to the transformers, and plug the gear into that. The advantage is that it helps avoid confusion as to which gear is 100 and which is 220. Keep USA cables attached to all 110 v gear, and you can only plug that in to the power strip. If you use normal UK cables and connectors, then you have the possibility of one day forgetting which is which, and plugging your 110 v gear into a 220v outlet. Been there, done that. The fireworks are quite entertaining! So keep all your equipment well identified, label all your gear and cables with "110 volt only", and think twice before you plug it in!

2. If so, will the 600watt auto transformer provide enough headroom for the speakers?

Yes. 50% margin is what I normally use, so you'll be fine with that. Keep things running cool.

- Stuart -

thanks Stuart,
I've had a quick google search for 110v power strips to buy here in Ireland and they do not seem to be available so my only option is to hard wire the power cables from the speakers into a junction box,

do you know, what ampage this junction box wud need to be?

Thanks
hally

I buy my power strips on e-bay and import them, but if you only need one or two, that might be expensive! Got any friends who might be traveling to/from the USA soon?

On power: If you are drawing 400 watts from 110 v then theoretically that is around 4 amps (depending on power factor, losses, etc.). But I would still wire it as a normal 15 amp circuit and put a 6 amp fuse in it somewhere, for safety. Of course, the current draw on the 220 volt side will be half of that, around 2 amps.


- Stuart -

Not all US style 60Hz power transformers will be happy operating at 50Hz.