Eurozone sickness and 230v single phase vs 240v two-phase.

European 230 volts is from hot to neutral (or grounded).

USA 240 volts has no neutral, it’s 120 volts for each leg. (120 volts is derived from grounding each leg).

If a European 230V transformer is wired to the grounded conductor, it’s a non-convertible and you can’t use it in a 240 volt US outlet. If the 230V transformer has two 115 volt primaries that can be configured to be commonly grounded in series or parallel, then it can run on either 240V or 120V. This is done by the user with jumpers or switching. You will have to up the fuse size if it can do 120V.

Note that the extra ten volts may or may not be a problem. If the secondary side of the power supply (DC voltage) capacitors are rated very close to that secondary DC voltage, the extra 10 volts will be a problem as it will raise the DC voltage by 14 volts. The 60 hz frequency should not be an issue with 50 hz amplifiers.

Technically, US 240V is 1 phase, but balanced. Appliances that use balanced power, like your dryer or range, should use double pole power switches and breakers which disconnect both legs of power at the same time.

Most modern equipment intended for 120V expects an unbalanced input, with only 1 fuse and only turns off 1 leg.

Most equipment won't know the difference.  I had a european Ayon amp that has a "phase" light on it to tell you if the plug is reversed.   The light lights up on US power but it works fine.  I got ahold of a european style transformer and it didn't change anything other than the light went out.

TRANSFORMER CAUTION:  Before you buy an expensive transfomer, I learned that many transformers that say they are made to run European equipment do not provide Euro convention power.  Instead of providing 230/240V and a neutral, they provide two 120V legs that are phased to be 240V to each other.  In other words, they provide US convention power.  Disappointing.  I returned 3 or 4 transformers before I found one that was true Euro power and caused the phase light to go off.

If you do go with a transformer, make sure it is oversized.

Jerry

… Disappointing.  I returned 3 or 4 transformers before I found one that was true Euro power and caused the phase light to go off.

Ok which brand was it?

Or does the OP need to order 3 or 4 themselves, do it all again?

@holmz I wouldn't recommend the one I ended up with.  It hummed badly.  It did confirm that the amp ran identically on 120v-120V legs vs 240V-0V legs but it was not good quality and I returned it.  It was Rockstone.  

A good solution would be a PSA Regenerator.  That is what I use now.  Mine is  120Vin--120V out.  I contacted them about the availability of 120V in--240V out and  they don't seem to make that.  So I told them that I have 240V us at my amplifier and asked about using the 240V US power to power a 240V version and they said the 240V version isn't available in the US due to some vague requirement.   Meantime I decided that the amp made too much heat for my un-airconditioned listening room and moved to another amp. 

But the amp ran fine plugged into wall power.

Jerry