Congratulations on your new toy!
check here for info on car installation; particularly the section Properly adjust the input gain level on the amplifier.

You should not take the volume past 0db for most listening settings. I have mine fixed to not go past 0 at all. Follow the procedures in the FAQ and let us know how things turn out.
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-- Murray I What part of 'no' don't you understand? Is it the 'N', or the 'Zero'?