@sv1hao:
A few clarifications. First, the OP is speaking specifically to the Kaboom. Not a generic boombox so generalities is not helpful. Other discussions have already taken place regarding this issue in general. For the record, the kaboom power supply on Mains supply 19.3v at the rails to the kaboom circuitry.
Secondly, our USA mains is seldom 110v. It's more like 120v and around here, it's more like between 122 to 127 volts. Today, I just measured voltage at 122 volts. I have never ever in all my years read 110 volts in this area. Last month, it was 127 volts. I think it's fair to say that our typical mains voltage here would be 22% to 27% higher than the 100v japanese voltage.
So while your theoretical 10/11 voltage ratio is, in your words, "no big deal." Let's change the voltages to real world voltages. For the kaboom, it would be more like 19.3/23.5 or 19.3/24.5. I would say a 4.2 to 5.2 volt increase is certainly substantial. And while typical electronic design will build in a little extra room for error, running it at 25 to 27% over specs continuously will certainly take it's toll over time on the regulators, of which the kaboom has many. Finally, while most of the digital circuits in the kaboom have exacting voltge regulators, the amps are fed the full rail voltage. This is typical for most boomboxes. I'm not going to suggest that the kaboom amps can't handle the extra 5 volts. However, I will say that when operated with higher than design voltage, and operated at or near max volume, the amps could be stressed and possibly blow prematurely. Amps will usually produce output commensurate with the supplied voltage. Higher input voltage usually means higher output potential. If designed that way with proper heatsinking, etc, no problem. If not, then watch out. The kabooms, even when operated at normal voltage generates lots of heat at the radiators. Are they sufficient to handle the excess? I dunno. Also, are the chips designed to operate safely at 24.5v? I dunno either. But suffice to say I'm not prepared to say it's no big deal. Remember, the kaboom has a 12v DC input. 24.5v is more than double that.