Audio Systems: car stereo, car electrics, stereo unit

Question
i have recently purchased a new car stereo and have had it installed. it plays fine for a little bit and the it starts to go quiet and fuzzy. i am in the process of changing the wiring and have upgraded the power source to the unit .....   what could the problem be?

Answer
There are too many possibilities.

It must be determined if the problem is internal to the stereo or its amplifiers OR external such as wiring or car electrics.

If you can give me the make and model of the vehicle, the make/model of the stereo unit I can give you a precise comment on what may be going on.

First thing that would alarm me, normally, is if you have used the right conversion harness for connecting all the speakers and power wires properly to the head unit.  A shorted speaker wire, for example, can certainly cause the amplifiers to "fuzz" out and shut down the amplifier.

Let me know more.
cleggsan