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I want to buy a 500W RMS surround system from the US and it is 120VAC.

I'm planning to use a transformer here but I'm not sure what is the size/specs of the transformer to use or will it going to work this way.. I need your expert advice on this matter.. :)

BTW, I visited local store to buy locally available converter but it is only 100Watts and I think it is too way lower of what I actually need.

This is how I'm going to get 120VAC from the transformer. enter image description here

keshlam
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mboy
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    Do you think it will work? And how do I size the transformer to be able to carry 500W? – mboy Dec 08 '15 at 16:03
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    Note that a "500W RMS" stereo doesn't necessarily consume 500W of electricity, so check the power consumption of the unit to make sure you're sizing the transformer correctly. – JPhi1618 Dec 08 '15 at 16:06
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    You're just looking for something like this, right? I guess your question isn't clear. Seems like you just need a "step down transformer". – JPhi1618 Dec 08 '15 at 16:09
  • @JPhi1618 yes!... i saw similar in the local store but it is only 100w.. Planning to DIY it like the image above to get 120vac – mboy Dec 08 '15 at 16:38
  • regarding power consumption I have another 150w amplifier and it is consuming around 250w of power according to my Watt meter – mboy Dec 08 '15 at 16:40
  • I'm not sure what that diagram represents in relationship to your project. In electrical systems that are natively 240v, that L2 line doesn't exist. In the USA, that diagram would be more meaningful. – JPhi1618 Dec 08 '15 at 16:42
  • Why not check the VA rating on the transformer in the amplifier? That's the most that the amplifier will ever draw. For that matter, why not just change the transformer in the amp for one of the proper voltage? It's a big job, but already you're talking about big (and expensive) changes, and then you won't have your power going through two transformer. – Joel Keene Dec 09 '15 at 05:08
  • @Joel Keene there are only four connections in the above diagram and transformers are cheap than I pay someone to convert and modify the amp.. :) – mboy Dec 09 '15 at 05:18
  • I'm voting to close this question as off-topic because it is about building a power supply for a piece of consumer electronics, not about home improvement. – Niall C. Dec 10 '15 at 15:45

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what you have drawn would work if sized correctly based on voltage. However the U.S. power is 60HZ, I thought you were on 50HZ. The lower frequency may cause issues with the amplifier filter circuits (audible hum or buzz) I would look into that first , then think about a “step down” transformer 2:1 .
The reason I would point you in that direction is the center tapped system would need at a bare minimum 2X the wattage. I usually over size transformers by 50% (wattage) to reduce the heat created and extend the transformer life. The power your unit requires to run is the important thing not the amplification wattage if it is a 500w amp it will take far more run the system than 500W.

Ed Beal
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    I'm on 220-240v 60Hz too.. step down transfromers like that in the diagram are easily available in my area but I cannot find somewhere in the internet how to size the transformer I need.. – mboy Dec 08 '15 at 22:31
  • you need to find the total power in watts the amplifer draws P=IxE using a center tapp transformer you will need at minimum 2x the wattage. power in the primary of a transformer is = to the power in the secondary but you are only using 1/2 the secondary so that is why I say it will need to be at least 2X or the transformer will burn up. – Ed Beal Dec 08 '15 at 22:44
  • I just looked at the one JPhi linked to and that would work if your total draw is 500W or less – Ed Beal Dec 08 '15 at 22:54
  • Yep.. The amplifier is 500 RMS and peak is 1000watts so just to be safe I want to get around 1000 watts transformer.. – mboy Dec 08 '15 at 22:56
  • P/E=amps 1000/220=4.54A if your system draws12A at 220V as you calculated above 2640 watts (1000W not enough) – Ed Beal Dec 08 '15 at 23:10
  • I will start from 6A because I have one lying here from an old power supply.. Thanks sir! – mboy Dec 08 '15 at 23:31
  • Watch the temp on the transformer if it gets hot you will need to go bigger. but if you have it,,, worth a try, it would be a good idea to put a fuse in your circuit so it dosent let the magic smoke out of the transformer. Good luck – Ed Beal Dec 08 '15 at 23:38