Audio Systems: Loud HUM with preamp and amp connected, ground loop isolator, power amp

Question
Thanks for your time!
Recently I bought a power amp (ADCOM 555-II) to use with preamp (Classe SSP-30).  But I hear a loud hum from both speakers with preamp and amp connected and I cannot use the power amp.  I have used preamp and it is just ok and the power amp looks ok itself.  I checked the cable and it looks ok too.  How can I fix this problem (loud hum) to use my preamp and power amp together?   I appreciate you for your time and great information.

Answer
usually when 2 pieces of equipment are fine by themselvs but hum together its a ground loop.  the esiest way to fix this is with a ground loop isolator.  you can get one at radioshack for about 20 bucks.  it's a little box that the RCAs connect to and it isolates them so that grounds cant interfere basically.  
Try that.  the other methods of fixing it are much more involved so try this first and see how it goes.

good luck and let me know ok?