solution for whining aftermarket radio
 

First of all, thanks goes out to George A. for the solution to the whining aftermarket radio. I have an 89 300se that I replaced the factory Becker with an aftermarket Nakamichi deck with a Sony xm radio. I immediately picked up a bad whine/buzzing that the faster you drove the car the higher pitched the whine. It was really annoying. Then, I talked to George who stated he replaced his factory with an aftermarket and rewired the speakers bypassing the rear amps. This solved my problem. Now, if you turn the radio down with no sound(but not off) you can carefully listen and hear a very slight buzz. But, under normal radio operation, even with soft classical music, the buzzing is almost non-existant. If you have this problem and need help, send me an email at scottfish@peoplepc.com and I will either give you instructions or forward you to George for assistance. Again, George A., thanks.

This can be caused by grounding components to different groundpoints or no filter for the power lead to the radio. I grounded my components to a common point and installed an inline noise filter for the hot lead to the radio and I have zero noise.