Audio Systems: car audio fault finding, amp input, channel amplifier

Question
hey again,
            i havefound out that all the speakers that are connected to my 4 channel amplifier (which are a pair of splits up the front and a pair of 6 inches at the back doors) are all cutting in and cutting back out. they dont completely cut in an dout but just drop off the volume a bit every now and then. when i turn the volume right down i can hear a fuzzy sound coming from the speakers. when the speakers cut out when the volume is on they go a bit fuzzy as well then when it kicks back in it goes back to being perfect. i have tightened all connections at the amp but it still does it. what do u think is wrong with it?

Answer
Well as its on all four speakers in must be common to all four so its either the amp or the radio as you say you have checked ALL connections and power etc. (you didn't say what head unit you have or if its on radio /CD or all sources).
I think the amp input level maybe too high and its tripping out, turn the little dial in the end of the amp down and that should be OK. If this fails then check the head unit, try and swap it with a known good one for a few minuets just to see, Or failing that your amp or head unit is faulty and again, a swap over is the quickest way to test.
Peter