Originally Posted by Gustav_H
I get an alternator wining on my MP3 player when the 12V adapter is connected. Otherwise it's the same good quality as the cd-changer. But it would have been nice to get rid of the wining when charging the MP3-player.
Any suggestions on reducing 12V depending wining?
The main problem is the ground loop....
Try to connect only the +12V to mp3 player.
Since the ground comes from RCA connectors too....
In this case You can hear only the mp3 player's noise...
(Since the small current what is flow through RCA shield can cause a small voltage drop... if this current is constant (case of portable mp3, i think near constant), you cannot hear noise...)
But take care! The RCA shield cannot supply high current!
Just for a small portable mp3 player...
The best solution is a differential driver...
Which can take a reference point from RCA shield, and add the music into this reference.
Analog Devices AD623 - Single Supply, Rail-Rail, Low Cost Instrumentation Amplifier
in the pdf page number 12 / Figure 41/b is the solution for example.
REF connect to RCA shield.
Vout to RCA input
Vin to mp3 player outout.
Vs connect to a filtered and regulated 3-5V supply...
Arnold