Originally Posted by Glimmie
Originally Posted by arnyk
If you go significantly under voltage a classic analog power supply can let a lot of noise though the power supply regulators.
I should add that if the device has an unregulated power supply and is run from 120v, the internal DC voltages will be higher. Too high? Depends. And even if the internal power supply is regulated and uses a power transformer, the filter capacitors could be overvoltaged - not likely but possible.
Regulator chips are now penny-ante jelly beans and probably cost less than electrolytic capacitors. Virtually every major internal power supply (except the power amps) in quality audio gear (even $40 DVD players) run off of regulators. Therefore, the first fatalities related to excess line voltages are often the regulator chips themselves.
I would not run any 100v device on 120v unless I was sure it had a switch mode power supply.
I've broken that rule with impunity for over 30 years.
Interestingly enough, those same $40 DVD players generally have a switchmode power supply with jelly bean regulators on the outputs.