Looking for a free way to add an AUX input into 06 mazda3
 

looking for a free way to install an aux jack
hey i was reading up on this for a while and am having a hard time finding a specific answer to the free option that requires soldering.

i have an 06 mazda3 5-door and am an electrical engineering major so i can solder.

i read some posts about soldering directly to the inputs in the bottom of the radio rather than putting the adapter in.

does anyone have a link or any info about what pins need to be utalized to do this?

thanks for your help