CD box whine through speakers

[project 911]

Hi All,

I'm trying to track down a problem with a stereo install. I'm getting a whine through my speakers from the Bosch CD box. The car doesn't need to be running, but just with the key on. If I unhook the inputs to my amp, it goes away, so I guess the problem isn't with the amp or speaker wires. The same thing happens with two different head units.

One suggestion I've seen is to use one common ground point for all the components.
Anyone else had this problem (and found a solution)?

Thanks for any help. The whine is driving me nuts...

[Early_S_Man]

Steve,

The Bosch CDI DC-to-DC inverter operates at approximately 3000 Hz, but, being a square-wave switching circuit ... it generates harmonics up through at least 30 kHz ...

Your amp problem needs to be treated as a typical RFI/EMI case at the engine electrical panel ... with bypass capacitors. My suggestion is to get some ceramic disk capacitors and install them on the back side of the electrical panel at the rear fuse block, at the red wire where the CDI unit draws its' power from.

I suggest three caps ... 0.01 mF, 0.05 mF, and 0.1 mf, all rated at 200 Volts.

If treatment at that single point doesn't cure the problem, then try another identical set of bypass caps at the amplifier power connection!

[bell]

if the caps do not work a second trick is to change the ground path for the rca's.
this can be done by adding a ground dirrectly to the rca shield where they plug into the amp......it's a hit or miss thing though, ground one end of the wire to the chassis of the car and touch the other to the shield of the rca.

[project 911]

Thanks for the help guys-