Add low-level tulp jack to headunit

[zzattack]

I had installed my audio amplifier using a high/low-converter because the standard radio doesn't come with low-level RCA/tulp outputs. Disappointed by the signal quality I decided to see whether we could just grab the low-level inputs before they hit the amplifier in the headunit.

Bad news for me was that the unit is really hard to disassemble beyond a certain point. I couldn't get a view of the amplifier circuit until I removed the metal shield/frame on the backside of the unit. This was soldered to the ground plane on multiple spots and was overall a very tight fit, but eventually I got it out. The allowed me to remove some more shielding, eventually revealing that the amplifier in question is a TDA7564B. This is a simple amplifier with an easily found datasheet including clear pinning information:




Now there's some good news for anyone else wanting to carry this out on the same radio. Knowing what amp you have there's no need to disassemble much at all. The unit comes apart with 8 clearly visible screws on the side, revealing the navigation (top) and radio (bottom) assemblies. All you need to do is temporarily remove two capacitors on the radio assembly to get some working room for your hands and iron. Then connect RCA cables to pins 11 and 12 for front-left and front-right respectively, and pin 13 for the ground. Reassemble and done