ok here is the deal:
99 audi a4 avant.
head unit number 1- eclipse avn7000
i have a crackle noise when the head unit is playing. for any output (dvd,radio,ipod,etc). it happened after i installed my amp and my ipod adapter. mainly more pronounced when i turn the volume up. not so much with it low. also the rear speakers are ran straight from the head unit.and the fronts are through the aftermarket harness. factory amp is completely removed

things i have tried:
checked grounds and power
disconnected amp and rcas,ipod adapter, antenna, all speakers except one and switched it around..the noise is on every speaker, changed the load reduction relay, checked harness, even put another head unit in, all to no avail. i even sent off the eclipse to get rebuilt for 175.00 thinking it was the head unit. but the new head (JVC) i put in for the time being is doing the same thing. please help! i need some tunes!