Feed back from radio when I shut it off

First off, please do not post multiple threads with the same question.  Thanks.

Now I've already answered your question, but let me try again.  Every head unit produces a different level output.  No two - not even two of the make and model - will be exactly the same.  An outboard amplifier has a gain control so that you can match it's input sensitivity to the output from your head unit.  SO, like I said before, an amplifier's gain setting will be different for every head unit, and there is nothing wrong with any of your gear that causes this, it is the nature of car audio equipment.  If you have the input gain too high on an amplifier it can overload the input stages and cause it to oscillate or make strange noise.

NOW, you have several problems going on here that make your installation difficult.  You are using factory head units, which are normally low to mid-level quality and not designed for adding outboard amplifiers easily.  This means you are using the speaker-level signals, which can be clipped, noisy and have unknown EQ added to them from the factory head.  Also, you are trying to use a factory CD-changer that did NOT come with your car, which can cause other problems that you may not even be able to predict...

How is the signal from the CD-changer getting to your amp?

Is your amp properly grounded?

And lastly, and man I hope I don't have to keep posting this, but something tells me it will remain the most common thing I write for many more years, AMPLIFIER GAIN IS NOT A VOLUME CONTROL!  It is to be set to match the head unit and left alone.  Any gain setting from all the way left to all the way right may be the CORRECT setting, depending on the head and input voltage levels.  1/4-way is probably the CORRECT setting (or as close to it as you seem able to accept) for your setup.  If this means you "don't get enough bass," then hey, it's time for new equipment as you cannot get blood from a stone.  I suggest the FIRST thing you do is go to a good car stereo shop in your town and buy a new head unit.  Pay for professional installation and amplifier matching, and then don't F**K with it!  If it's still "not enough bass," then you will know you also need a different subwoofer setup.

Hey,  I thank you once again for all the help, but I now have the actual answer.  The actual wire for the two units are a bit dif.  There were two wires set differently for this model.  You are correct that the gain will solve the problem, but it really was not the solution.  I have all the radio wire diagrams and I seriously can say that I feel like I have gained the proper knowledge now to know what and where things went wrong. 

Once again thank you and Sorry for the multiple listings, but I am new and was familliar with the forum.  :)