A8002T amp

I have an audibahn A8002T amp wired to an AW1206T 12 audiobahn flame q sub.  I had a few questions that I needed answered.  I still have my stock headunit in there, but I've noticed when I turn my stock head uynit off it makes this constant bass buzz till I turn it back on.  It doesnt really bother me that much unless I accidently turn it off, but never the less its still a problem.. Can anyone give me more info on setting my amp.  I had it done at circuit city but they did some crappy work since they fried my first amp the morn after install..  Im not much of an audio guru so all the help that you can give will be much appreciated.  I need info on what sub sonic, LPF, the level setting, Phase Shift.  And one more thing about setting.. how do I know which way to turn the variables.....

thanks,

 - Blaze.