I am using a stepup transformer to run 220V components on 115V lines in the USA. I have two questions:

1. Does the transformer itself waste any/much energy, and

2. Are there inherent hum or other audio issues in this kind of situation?

Thanks!

If you are using a step down transformer do you hear anything that concerns you?

All transformers have looses. In conventional transformers with laminated cores (E-I types from the shape of the laminations) hysteresis and eddy current losses in the core are the chief factors no/low load factors. Resistive I x R loss increases with load.

Toroidal transformers have a much lower no/low load loss.

How much loss? Loss varies with load; even a transformer with no load has consumes a bit of power. But its fair to say that transformers at house power voltages are >85% efficient even for small ones to >95% for larger ones.

There is a potential for inductive hum with any transformer, but step up and step down transformers are normally not close enough to the chassis to cause a problem. The transformer itself may hum if it is an E-I design.

Are eddy currents that much of a concern with the frequency of standard ac current in the USA?

Are eddy currents that much of a concern with the frequency of standard ac current in the USA?

They exist, but I admit that it has been a long while since I did any math on transformers, so I won't speculate as to what percentage they contribute to loss. I just wanted to provide a general idea of what was involved; that and I like the word hysteresis, it reminds me of the days of youth when turntable makers would crow about the kind of AC motor used; hysteresis-synchronous being the best.;)

Thanks all!