Audio gear such as amps, preamps, tuners, CD players etc typically have transformers inside. Whatever the line in voltage is, that line in voltage is changed to whatever the component actually runs on
100v,115v versus 230v
Some audio technicians/ enthusiasts claiming that, high end audio equipment performs much better european 220/230v even 240 UK voltage if that's the case why USA 110V / 120 volt AC ?