Using step up / down transformers?

I want to add that one experience that I had using a step up transformer was that my line voltage is 120 volts or so, and then measured AFTER the transformer it was 240 volts. I suppose that makes good sense BUT, the Cayin CD22 CD player being used did not think so. It accepts 220 volts, and with less for a margin/deviation than what it was given. Bottom line, repair of the CD player was needed.
My fix was to either use variac in front of the step up transformer, or use a PS Audio power plant in front of the step up transformer. In both cases I would adjust the voltage feeding the step up transformer to about 110 volts. This of course resulted in the CD player getting 220 volts.
The good news is that the player sounds so great, all of this fuss is worth it. Maybe there is a step up transformer wound a bit differently on the secondary that would make this a non issue in the first place.

Let's say that a 120 volt line (load) is drawing 10 amps. Since it is a single ended design, the draw will be carried by the hot conductor. 
 By the same token, using the same example of a 10 amp draw, a 220 volt line will still draw (or I should say the load will draw) 10 amps total, BUT since it is a Balanced design, each conductor would be drawing 5 amps. The total is the same. The word efficiency, may be applied to the fact that a smaller gauge wire can then be used. 
 I have heard however that there is an increase in efficiency of electric motors because the power is coming at opposite phases (times).