Nope. And there's a good reason for it too. If it were reversed, when you plugged in the amp, you could either short the amp to ground, or send a fair amount of voltage through your fingers! Not likely enough to kill you, but it could piss you off
the only real problem would be your speakers running with reversed polarity. which isnt really a problem, as long as everything else is running with the polarity reversed. and if you're using JBL's, there's a good chance you'd now be running it in "normal" polarity anyways!