157000 km on the
Join Date: Jun 2007
Re: High pitched noise whilst playing CD's
Does it alter with engine revs? If so, it most likely origins from the generator. I have it too, mostly noticable when playing CD´s that are mastered with lower output. Then I turn the volume knob up, increasing the gain and the sound becomes audible.
This is a engineering flaw no doubt. I´m almost certain it is in fact a ground loop that only affects the sound from the CD as it´s routed to the back of the car. If the CD was grounded in the same spot as the ICS it would never happen. So a possible solution would be re-routing the ground return wire to the point where the ICS is grounded. Or, separating the audio ground from the supply ground could do the trick. Remember somebody replacing a blown resistor in the ICS, and the CD noise disappeared at the same time. Could be the resistor was replaced with the "wrong" value, affecting the ground. In regular audio equipment, the signal ground and supply ground are usually separated with some resistance, forcing any ground noise to occur across the resistance rather than in the signal path. Simple and effective.
If anybody has a electronics schematic diagram we may come up with a solution.
Noise suppressors are never necessary! There is always a reason for the noise occurring in the first place, and it´s much better to find it and fix it rather than trying to get rid of the symptoms with filters. They always deteriorate the sound quality to some extent.