>>I think electromechanical stuff, like motor drives, could be affected by this. I seem to remember reading that the motors in at least some mellotrons took particular exception to receiving the wrong frequency.<<
only the older machines with mains driven motors; the more common m400 has a dc motor & a servo somewhat akin to those found in decent 1/4" machines like revoxes. but the same issue (50Hz/60Hz) might also affect hammond tonewheel organs.... a lot of cheaper 1/4" machines & a great many turntables also used synchronous motors that rely on mains frequency for speed regulation. dreadful idea.
fwiw, I run a great deal of audio & midi equipment by feeding regulated 8V around on the spare wires in my midi connections. the 8V comes from a sony camcorder supply which works off anything from 80-300V ac & (not that I've tried it) any frequency. it says.
I carry a spare.
the exceptions are a couple of alesis boxes (s4+ module, quadraverb) where I've had to source a suitable mains transformer.... there was room inside the s4+ for a little toroidal transformer, fuse & so forth, & I put a 110/220 switch in there too. & there's enough capacity for it to power the quadraverb via a link between the original dc jacks on the two modules. I label the back of the gear whenever I've opened it to change the voltage. my alesis mixer had a dual-primary transformer already, so I just added a switch to make it 110/220 compatible.
the two jam-mans, at the moment, need different power units for 110 & 220 operation. I am trying to find a small-enough switching supply to fit inside the jam-man itself..... but the jam-man appears to be one of those awkward boxes that does something else with the 9V ac supply besides turn it into 5V dc. I hate wall-warts, especially on stage. I know they save the manufacturers (& us?) some money, but they absolutely suck in an environment that could in any way be described as "professional".
duncan.
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