It all depends on whether the equipment has a regulated power supply or not. A piece that I just bought does have a regulated supply, and, according to the owner's manual, will function properly with ac voltage from 92 to 130 volts, 50 or 60 Hz.
As Jeffreybehr says, even without a regulated supply a power amp ought to be OK.
As Jeffreybehr says, even without a regulated supply a power amp ought to be OK.