Converting Mark Levinson gear from 240V to 120V

i have the same problem as you have and i wrote madrigal to ask for their help.
they told me that they will only do it at their factory in connecticut for about $150 per piece or you can have it done by a dealer in your country outside the us.
since i live in hong kong and am moving back to the us, i wanted to have the job done properly and tested so if i have it done in hong kong, i won't know if they did it properly by testing it. then again i don't want to be shipping all my mark reference components to get it done either, the 33's are quite heavy to ship. i asked madrigal to send someone for a field job but they said that they don't do that.
i don't want to run the equipment on step down converters. it looks like i will have the dealer here do it and take a chance. the dealer here atleast does field jobs. let me know what you do.

As far as I know, most of the power transformers used in audio-gear assumed to work on both 240 and 120V. Most of them have an extra output set that even no manufacturer can get rid of. Manufacturers to hide this fact from illiterate consumer can make money without extraneous part and labor investment. Madrigal in this case can be on my "Crook list" charging $150+....
I do suspect that Madrigal speculating on these piece-of-cace issues since they largely deal with Europe and less-likely will they use different transformer.

The bottom line is that if voltage is measured accross each of output windings of power transformer at the same input AC voltage they will be different in relation of 2:1(120V terminals v.s. 240V terminals. It lies in the simple ideal transformer formula:
Vin/Vout = Nin/Nout where N is the number of solenoidal winds and V is input and output voltage respectively.

If it's just a matter of re-plugging different wires from the same transformer it can only take 10...15min depending on skills of technician.

Why not run a dedicated 240V line from your electrical box? Simpler and the equipment would probably run better anyway.