I have just upgraded from a factory HU to a aftermarket 4 channel amp.
The amp is an MTX TC4004, the speakers are newish.
The noise happens when I use my new EQUALIZER.
If i bypass the EQ and run the line out converter directly to my MTX amp the noise IS GONE!!
BUT the EQ has an alternator noise and a sort of STATIC noise, the alt noise increases when the engine revs.
Initially I thought that this could be a Grounding issue, so I changed the ground and a proportion of the problem ceased, HOWEVER the noise is still audible at low volumes and the static, white, background noise is audible at times AND in between songs.
What do you guys think? THIS ONE IS BEYOND ME!!!