That is a question similar to one I asked on the PSW forum. I never got a straight forward and definitive answer. The summation of many replies was "it is probably not a big deal, BUT it is best to do it right". Making a special cable or buying a reversing adaptor are options. Just make sure that you label them, so they don't get used as a standard cable.
Here is the link, if curious.http://forums.prosoundweb.com/index.php ... 570.0.html
Thanks for your reply guys.
With regards to the jumper to change polarity, I don't think there's any. There's just a strip that says " signal ground lift ".
I was just wondering, why would Crest Audio make an amp with pin #3 positive when almost all other equipment have pin #2 positive??