Thanks for the help, guys. Jea48, even if I did that it can't be maintained with a three prong connector. Yeah, the best solution would be to pack them off and have them rewired to play together. I hate shipping them as one already has chassis damage from mishandling.Dan the polarity orientation check is only a test to make sure the manufacture of the amp checked for proper polarity orientation of the primary winding of the transformer before it was wired to the circuit.
If the test shows one of the amps power transformers has reversed polarity the next step is to check the power cord, if detachable IEC connection, and make sure the polarity of the cord is correct. Especially in the case of an aftermarket non UL or CSA listed power cord.
Next step if the power cord/s checks ok and the problem is the amp I would then try a real word test of the system and check for the ground loop hum.
Remove the ground cheater on the good amp. For the test the amp that needs the polarity reversed install the ground cheater into the wall outlet that gives the lowest voltage reading of the two.
Next connect the ground of the cheater to earth ground. (equipment ground at the wall outlet).
Turn system on and check for hum. IF hum is gone then the next step is to correct the problem.
The correct procedure is to reverse the primary leads connection inside the amp. Who better to do the job than the manufacture. Good chance he will only charge you for shipping.
You could also take the amp to a reputable repair tech.
There is no guarantee the hum problem is caused by a polarity reversed orientation. The test will require a little of your time and hopefully find the problem.
Or you could just buy a Jensen isolator for one or both ics.
Contact Jensen, bet they would be glad to help.