Wouldn't the consumption be slightly worse for the 240/250V version as there'd be more heat loss in the primary? Besides that, the average of output in RMS to consumption as a ratio seems - from a quick glance at the boxes I have standing around - to be around a third of the amount it consumes if the mains supply were even relevant, which it isn't.
This JVC of mine is a 12V box that consumes 62 Watts (see label top of the back left of the cable guard as you see it) and has a power output of 11wpc in real (RMS) Watts. That this box is run on a mains supply that regularly reaches 260VAC at off peak times and averages 253VAC makes no odds, it's supply is
12VDC from either its 8 Ds or the secondary of its (original) PSU.
(& LB is a UK-spec version in this case, I checked the TX from my spare one of these and its windings, when compared to each other, suggest that in spite of it saying 240V on there it is going to provide a steady 13.8VDC from the 250V supply so is it not just as likely that the 100V version of the M90 has the same TX in its PSU as the 117V version? The percentage difference is only slightly greater between 220 and 253 than it is between 100 and 117. It's only Euro-spec boxes that I've found wanting with their 220V secs failing when connected to a larger pd at the floor).
