Step up converter for a stereo

I'm going back to the US soon and am bringing my stereo from the UK with me.  This is the only appliance I'm bringing and want to get a step up converter for it so I can use it there.  What do I need to know before I order one - is there a wattage range I need to quote?  I'm just afraid of buying one and then finding out it won't work.  Sorry if this is a dumb question - I'm not very up on electronics.

Have a look at the label (or stamped, molded equivalent) on the back of the unit(s) and it should tell you the maximum power rating, either in watts (W) or volt-amperes (VA).   For audio equipment there will be no added complications, so you just need a transformer which matches or exceeds that rating (or the total of the ratings if you have two or more separate pieces of equipment).

Unless it's a huge setup or you're running extremely powerful amplifiers, a 300VA unit such as this one will almost certainly be sufficient:

http://www.airlinktransformers.com/transformer/uk320-british-240volt-stepup-transformer.asp

I believe what you want is a step DOWN convertor.  Not a step up.  You want to go down in current from 240 to 110.  However, look to see if your appliance is listed as 110/240 Volts because if it is, you will only need a plug adapter.  I bought two convertors with me from the states and am now realizing I didn't even need them.  My computer and other appliances that I brought can accept either 110 or 240.  It's just the plug that won't fit.  Wish I had found this forum before I came over. 

I believe what you want is a step DOWN convertor.  Not a step up.  You want to go down in current from 240 to 110.

Geeta has it the right way round.   To run a 240V appliance on 120V power you need a step-up transformer. 

120V into transformer, 240V out = Step-up
240V into transformer, 120V out = Step-down

I'm going back to the US soon and am bringing my stereo from the UK with me.

To run a UK 240v appliance on 120v in the US, you need to step the voltage down. (240 is greater than 120)

To run a UK 240v appliance on 120v in the US, you need to step the voltage down. (240 is greater than 120)

As Paul and geeta have correctly said, it is step up.

The mains voltage out of the wall is 120V, but the stereo will only run on an input voltage of 240V, therefore the 120V coming out of the wall has to be increased to 240V in order for the stereo to work (step up converter).

You don't reduce the appliance voltage to fit the US mains, you increase the US mains to fit the appliance voltage. And in the UK, you have to reduce the mains (240V) to fit the appliance (120V) - which is a step down converter.

You are correct.  I read her post backwards.  Thought she was going US to UK. 

Yeah, it's definitely step up.  Thanks Paul - I'm wondering if I can find it cheaper in the US...

You are correct.  I read her post backwards.  Thought she was going US to UK. 

I read it the right way, but still managed to give the wrong answer! Sorry about that.

Geeta, I've seen them on amazon (US), from UK to US, they look pretty decent, but its hard to tell.

I'm wondering if I can find it cheaper in the US...

Yes, although you might have to search a little longer to find one with a U.K. outlet instead of French/German/other European.    This would be the sort of thing you need:

http://www.international-electrical-supplies.com/transformers4.html

(I've never had any dealings with this place, so I can't vouch for them in any way.)

Wow, that's great - thanks a lot, Paul.  And thanks, L.

Just remember that you could run without a transformer at all if you happen to want to use the equipment near to where there is a spare 15 or 20A 240V outlet in the house.