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Variac vs. Isolation vs. Balanced Transformer? ALL

Hi,
I am looking into the different types of power transformers to fix a few things.

First is a slight hum from speakers using Class A ultra wide bandwidth amplifiers, caused by common mode noise between the Ground and neutral lines from my understanding.

This is not really all that critical as its well under noise heard 3 feet away, but we are picky otherwise we would not be on this site!

Second and maybe even more important is I am getting a pretty continuous 128 volt output from all my outlets. I would like to use a product or build one to step this down to the best possible 117 volts or so for most gear.

I see many variacs for about 100 bucks on the ebays etc... That can do at least 500 watts or 5 amps each.

I was considering just buying about 3 of these one for each mono block would cover the amps, and one or 2 more for the source components.

Anyway that's really the basis of the question, I will not pay 2000 for a used or new piece of gear, like a regenerator or powerplant etc...

I do not want to restrict the dynamics to the amps or other gear.

And I can not put just one unit at this point due to running power cables are in 3 different spots in the room and I will not be running 15 ft power cables all back to one point. Also due to the fact I prefer to split this all up over 2 or 3 circuits in the house anyway.

So where to go?
I see Balanced transformers, are these considered "Isolation" transformers as well? Also will these automatically put out a continuous voltage at the 115 to 117 range? Or would you still need a variac to adjust to the needed voltage and frequency?

Thanks
undertow

Showing 1 response by hevac1

hevac1
812 posts
 
Guys do not forget it is going to cost money just to power the coils of these items, even with no load. Also most transformers above 1kva will not like being turned off & on and can trip breakers on inrush. It is better to leave them on all the time but again at a cost.

I had a GE 5kva 240vac to 120vac balanced center tap transformer and it drew 5 amps just charge the coils on power up with no load. I was told by the GE that the draw is normal. I even tried switching it on and off via a starter but it tripped the 40 amp breaker 3 times out of 10. I wanted to try fuses but the type required cost too much to risk for testing, $30 each 5 minimun per order, they are used in most VFD's.

Too much cost for me, I use PS Audio equipment if I need volt or Hz control. It may cost more but they worked out the bugs and it can be turned off & on at will, by button or the new ones by remote.

I did not read all the issues here but Variacs do not change hertz only voltage and can hurt the a/c motor on your TT if connected to it.
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