Forum: Analog Circuits Blaupunkt CAR300(F) audio input modify

von Christensen C. (Company: no) (christensen)

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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.

von Christensen C. (Company: no) (christensen)

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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.

von Tommi (Guest)

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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.

von Russian (Guest)

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Respected, Tommi, explain please more particularly where there should be 
a bridge and where the manual switch. (google-translator)


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