Hi, I've try to modify an Blaupunkt CAR300(F) radio/cassette player to accept the portable mp3player. I’ve eliminate the mechanical tape part and the tape head reader amplifier (LM833). After that I’ve inject the signal to the inputs 2 of audio processor TDA7433D(pins: 2 and 3). At the input of the audio processor I have one 1uF capacitor/channel. The switching is working but it have a very annoying noise of whistle on the background. Can somebody help me to eliminate this annoying noise please. Thanks you in advanced.
Damn how stupid I am … the ground(-) was the problem. When I’ve search to connect for the ground the player was off, but when I've turned on, on the chosen connection point appeared a voltage difference and that’s make that noise.
Criss, according to Your instructions I also modified my Blaupunkt CAR300, it worked well! To all: I didn't use extra capacitors, but connected the lines to the existing capacitorsdirectly before the input pins. To switch the source, there are two mechanical switches inside the cassette deck. One can be bridged, then the other can be used as manual switch.
Respected, Tommi, explain please more particularly where there should be a bridge and where the manual switch. (google-translator)