AC line voltage in Japan is 100V. Don't you mean the SACD player you're considering is 100V, not 220V ? The current requirement of an SACD player is not much, so any small 120V to 100V converter should work fine, without hum or buzz because of its diminutive size. Frequency would only be a problem with devices containing synchronous motors that depend on AC line frequency to maintain rotational speed.
