amp via transformer 220 - 110 a good idea?


Hi, I'm wondering if connecting a ROTEL amp made for the US market (110V) to 220V via a standard step down transformer is a good idea. I read a lot about power supplies' having influence on sound quality but in this case it shouldn't probably make much of a difference in terms of noise whether you use a transformer or connect stuff directly to the outlet. I'm not an expert though so any sort of advice would be greatly appreciated. Thanks!
Maciek
malickia
Semi, you had disappointing results but you don't say anything about the transformer setup you were using. What was its power rating ( in VA, which are more or less equivalent to watts ), and its make ? How much power did your amp draw ?

Malickia, Pauly suggests you use a tranny 10 times too big. I wouldn't go quite so far--I would be comfortable with 3 times oversize and I would be willing to try 2 times--but 10 times oversize ( heavy ! ) would certainly do no harm. The idea is to make sure the transformer's iron core will never saturate and limit current.

The best transformers use oversize cores anyway; my two Topaz ultra-isolators weigh twice as much ( for their power rating ) as the others I use in my second system.

For more info about iso transformers, look for posts in the archives by Sean and Lak.
Malickia. A transformer can work fine and actually give an improvement in sound. What you need to do is to get one that is totally over-spec. i.e. 10 times what your amp is going to require otherwise you’ll end up having the issues Semi describes.

An isolation transformer could drop your noise by 6db and if you have electronic savvy and wire your own, you could wire the secondaries so that you get balanced out.

Have a look at Bruce R’s power supply at http://www.transcendentsound.com/power_supply.htm. He’s is 110 to 110, but you could do something similar with a step down tranny.

Regards
Paul
Thanks for your posts guys. I must admit though that I'm even more confused than in the beginning, as you expressed two completely opposite opinions. Cheers,
Maciek
I was doing the same thing for a while after taking on a short term assignment in a foreign country. I thought the sound was degraded in many ways. Less dynamic, transparency, top end rolled off early, sound stage was narrower.

I will suggest getting an used 220V amp while you are there and sell it at a small loss so you don't have to deal with voltage issue. In addition to lower sound quality, you also might face premature hardward failure which happened to me. Some equipments are easy to switch voltage and you can bring back to the state afterward.
IF the transformer is big enough to handle twice the current draw of the amp (more wouldn't hurt) and of reasonable quality, you should notice no degradation in its sound. As a side benefit, you might well get extra noise reduction--useful if your AC line carries a lot of crud.